POSIX compliance fix: make 'unalias' a regular builtin

Both 'alias' and 'unalias' are specified as regular builtins. Among
a few other things, that means it ought to be portable to use these
names for shell functions. But ksh93 disallowed that until now.

src/cmd/ksh93/data/builtins.c:
- Make 'unalias' a regular builtin by removing the BLT_SPC flag.
- (same fix for 'alias' was already done in afa68dca)
- Add the BLT_ENV flag to the 'alias' and 'hash' commands. In
  include/name.h, this flag is commented: "non-stoppable, can
  modify environment". The "non-stoppable" bit seems like a good
  idea: these operations should not be interruptable as that would
  cause an inconsistent state.

src/cmd/ksh93/sh.1:
- Remove the '-', indicating special builtin, from 'alias' entry.
- Minor cosmetic fix: space after the '-' for 'unset'.

(cherry picked from commit a4315d7672204acb543010b4d4916b22dcb9cb08)

NEWS

@@ -4,6 +4,12 @@ For full details, see the git log at:
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2020-06-11:
+
+- POSIX compliance fix: It is now possible to set shell functions named
+  'alias' or 'unalias', overriding the commands by the same names. In
+  technical terms, they are now regular builtins, not special builtins.
+
 2020-06-10:
 
 - The 'hash' utility is now a regular builtin instead of an alias to

src/cmd/ksh93/data/builtins.c

@@ -56,7 +56,7 @@
  */
 const struct shtable3 shtab_builtins[] =
 {
-	"login",	NV_BLTIN|BLT_ENV|BLT_SPC,	Bltin(login),
+	"login",	NV_BLTIN|BLT_ENV,		Bltin(login),
 	"exec",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(exec),
 	"set",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(set),	
 	":",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(true),
@@ -76,11 +76,11 @@ const struct shtable3 shtab_builtins[] =
 	"local",	NV_BLTIN|BLT_ENV|BLT_SPC|BLT_DCL,bltin(typeset),
 #endif
 #if _bin_newgrp || _usr_bin_newgrp
-	"newgrp",	NV_BLTIN|BLT_ENV|BLT_SPC,	Bltin(login),
+	"newgrp",	NV_BLTIN|BLT_ENV,		Bltin(login),
 #endif	/* _bin_newgrp || _usr_bin_newgrp */
-	"alias",	NV_BLTIN,			bltin(alias),
+	"alias",	NV_BLTIN|BLT_ENV,		bltin(alias),
-	"hash",		NV_BLTIN,			bltin(alias),
+	"hash",		NV_BLTIN|BLT_ENV,		bltin(alias),
-	"enum",		NV_BLTIN|BLT_ENV|BLT_SPC|BLT_DCL,bltin(enum),
+	"enum",		NV_BLTIN|BLT_ENV|BLT_DCL,	bltin(enum),
 	"eval",		NV_BLTIN|BLT_ENV|BLT_SPC|BLT_EXIT,bltin(eval),
 	"exit",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(return),
 	"fc",		NV_BLTIN|BLT_ENV|BLT_EXIT,	bltin(hist),
@@ -88,7 +88,7 @@ const struct shtable3 shtab_builtins[] =
 	"readonly",	NV_BLTIN|BLT_ENV|BLT_SPC|BLT_DCL,bltin(readonly),
 	"shift",	NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(shift),
 	"trap",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(trap),
-	"unalias",	NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(unalias),
+	"unalias",	NV_BLTIN|BLT_ENV,		bltin(unalias),
 	"unset",	NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(unset),
 	"builtin",	NV_BLTIN,			bltin(builtin),
 #if SHOPT_ECHOPRINT

src/cmd/ksh93/include/version.h

@@ -17,4 +17,4 @@
 *                  David Korn <dgk@research.att.com>                   *
 *                                                                      *
 ***********************************************************************/
-#define SH_RELEASE	"93u+m 2020-06-10"
+#define SH_RELEASE	"93u+m 2020-06-11"

src/cmd/ksh93/sh.1

@@ -7738,7 +7738,7 @@ option causes the mode to be printed as a symbolic
 value.  Otherwise, the
 mask is printed in octal.
 .TP
-\(dg \f3unalias\fP \*(OK \f3\-a\fP \*(CK \f2name\^\fP .\|.\|.
+\f3unalias\fP \*(OK \f3\-a\fP \*(CK \f2name\^\fP .\|.\|.
 The aliases
 given by the list of
 .IR name s
@@ -7748,7 +7748,7 @@ The
 option causes all the
 aliases to be unset.
 .TP
-\(dg\f3unset\fP \*(OK \f3\-fnv\fP \*(CK \f2vname\^\fP .\|.\|.
+\(dg \f3unset\fP \*(OK \f3\-fnv\fP \*(CK \f2vname\^\fP .\|.\|.
 The variables given by the list of
 .IR vname s
 are unassigned,