enum: remove arbitrary one-argument limitation

b_enum() contains a check that exactly one argument is given:

237:	if (error_info.errors || !*argv || *(argv + 1))

But the subsequent argument handling loop will happily deal with
multiple arguments:

246:	while(cp = *argv++)

Every other declaration command supports multiple arguments and I
see no reason why enum shouldn't. Simply removing the '*(argv + 1)'
check allows 'enum' to create more than one type per invocation.

src/cmd/ksh93/bltins/enum.c:
- b_enum(): Remove check for >1 args as described above.
- Update documentation to describe the behaviour of enumeration
  types in arithmetic expressions and to add an example: a bool
  type with two enumeration values 'false' (0) and 'true' (1).
  That type is predefined in ksh 93v- and 2020. We're not going
  to do that in 93u+m but it's good to document the possibility.

src/cmd/ksh93/sh.1:
- Make changes parallel to the enum.c self-doc update.

NEWS

@@ -3,6 +3,10 @@ For full details, see the git log at: https://github.com/ksh93/ksh/tree/1.0
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2022-03-05:
+
+- The 'enum' command can now create more than one type per invocation.
+
 2022-02-23:
 
 - When reading input from the keyboard, ksh now turns off nonblocking I/O

src/cmd/ksh93/bltins/enum.c

@@ -20,21 +20,33 @@
 ***********************************************************************/
 #include	"defs.h"
 
-#define ENUM_ID "enum (ksh 93u+m) 2021-12-17"
+#define ENUM_ID "enum (ksh 93u+m) 2022-03-05"
 
 const char sh_optenum[] =
 "[-?@(#)$Id: " ENUM_ID " $\n]"
 "[--catalog?" ERROR_CATALOG "]"
 "[+NAME?enum - create an enumeration type]"
-"[+DESCRIPTION?\benum\b is a declaration command that creates an enumeration "
-    "type \atypename\a that can only store any one of the values in the indexed "
-    "array variable \atypename\a.]"
+"[+DESCRIPTION?\benum\b is a declaration command that creates one or more "
+	"enumeration type declaration commands named \atypename\a. Variables "
+	"of the created type can only store any one of the \avalue\as given. "
+	"For example, \benum bool=(false true)\b creates a Boolean variable "
+	"type of which variables may be declared like \bbool x=true y=false\b.]"
 "[+?If the list of \avalue\as is omitted, then \atypename\a must name an "
     "indexed array variable with at least two elements.]" 
-"[+?For more information, see \atypename\a \b--man\b.]"
+"[+?For more information, create a type, then use \atypename\a \b--man\b.]"
+"[+USE IN ARITHMETIC EXPRESSIONS?When an enumeration variable is used in an "
+	"arithmetic expression, its value is the index into the array that "
+	"defined it, starting from 0. Taking the \bbool\b type from the "
+	"example above, if a variable of this type is used in an arithmetic "
+	"expression, \bfalse\b translates to 0 and \btrue\b to 1.]"
+"[+?Enumeration values may also be used directly in an arithmetic expression "
+	"that refers to a variable of an enumeration type. "
+	"To continue our example, for a \bbool\b variable \bv\b, "
+	"\b((v==true))\b is the same as \b((v==1))\b and "
+	"if a variable named \btrue\b exists, it is ignored.]"
 "[i:ignorecase?The values are case insensitive.]"
 "\n"
-"\n\atypename\a[\b=(\b \avalue\a ... \b)\b]\n"
+"\n\atypename\a[\b=(\b \avalue\a ... \b)\b] ...\n"
 "\n"
 "[+EXIT STATUS]"
     "{"
@@ -234,7 +246,7 @@ int b_enum(int argc, char** argv, Shbltin_t *context)
 		break;
 	}
 	argv += opt_info.index;
-	if (error_info.errors || !*argv || *(argv + 1))
+	if (error_info.errors || !*argv)
 	{
 		error(ERROR_USAGE|2, "%s", optusage(NiL));
 		return 1;

src/cmd/ksh93/include/version.h

@@ -21,7 +21,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-beta.2"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2022-02-23"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2022-03-05"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2022 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh.1

@@ -6392,10 +6392,13 @@ See
 .IR echo (1)
 for usage and description.
 .TP
-\(dd \f3enum\fP \*(OK \f3\-i\fP  \*(CK \f2type\^\fP\*(OK=(\f2value\^\fP .\|.\|.) \*(CK
-Creates a declaration command named \f2type\^\fP that
-allows one of the specified \f2value\fPs as
-enumeration names.  If \f3=(\fP\f2value\^\ .\|.\|.\|\fP\f3)\fP is
+\(dd \f3enum\fP \*(OK \f3\-i\fP \*(CK \f2type\^\fP\*(OK=(\f2value\^\fP .\|.\|.) \*(CK .\|.\|.
+Creates, for each \f2type\^\fP specified,
+an enumeration type declaration command named \f2type\^\fP.
+Variables of the created type can only store any one of the \f2value\fPs given.
+For example, \f3enum bool=(false true)\fP creates a Boolean variable
+type of which variables may be declared like \f3bool x=true y=false\fP.
+If \f3=(\fP\f2value\^\ .\|.\|.\|\fP\f3)\fP is
 omitted, then \f2type\^\fP must be an indexed array variable with at
 least two elements and the values are taken from this array variable.
 If
@@ -6412,6 +6415,14 @@ Within arithmetic expressions (see
 above), enumeration type values translate to index numbers between 0 and the
 number of defined values minus 1. It is an error for an arithmetic expression
 to assign a value outside of that range. Decimal fractions are ignored.
+Taking the \f3bool\fP type from the example above,
+if a variable of this type is used in an arithmetic expression,
+\f3false\fP translates to 0 and \f3true\fP to 1.
+Enumeration values may also be used directly in an arithmetic expression
+that refers to a variable of an enumeration type.
+To continue our example, for a \f3bool\fP variable \f3v\fP,
+\f3((v==true))\fP is the same as \f3((v==1))\fP
+and if a variable named \f3true\fP exists, it is ignored.
 .RE
 .TP
 \(dg \f3eval\fP \*(OK \f2arg\^\fP .\|.\|. \*(CK