Fix multiple problems with the getconf builtin (#280)

This commit fixes three problems with getconf pathbound builtin:
1. The -l/--lowercase option did not change all variable names to
   lower case.
2. The -q/--quote option now quotes all string values. Previously,
   it only quoted string values that had a space or other
   non-shellsafe character.
3. The -c/--call, -n/--name and -s/--standard options matched all
   variable names provided by 'getconf -a', even if none were
   actual matches.

Additionally, references to the confstr and sysconf functions have
been updated to reference section 3 of the man pages instead of
section 2.

src/lib/libast/port/astconf.c:
- Previously, only values that had spaces in them were quoted. Change
  that behavior to quote all string values by using the FMT_ALWAYS
  flag. Bug report: https://github.com/att/ast/issues/1173
- Not all variable names were printed in lowercase by 'getconf -l'.
  Fix it by adding a few missing instances of fmtlower.
  Bug report: https://github.com/att/ast/issues/1171
- Add the missing code to the '#if _pth_getconf_a' block to handle
  -c/-n/-s while parsing the OS's native 'getconf -a' output. This
  approach reuses code for name matching from other parts of
  astconflist(). Resolves: https://github.com/ksh93/ksh/issues/279

src/lib/libcmd/getconf.c:
- Update the documentation to note the -q flag only quotes strings.

src/cmd/ksh93/tests/bulitins.sh:
- Add regression tests for the getconf bugs fixed in this commit.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

src/lib/libcmd/getconf.c

@@ -27,7 +27,7 @@
  */
 
 static const char usage[] =
-"[-?\n@(#)$Id: getconf (ksh 93u+m) 2021-04-09 $\n]"
+"[-?\n@(#)$Id: getconf (ksh 93u+m) 2021-04-20 $\n]"
 "[--catalog?" ERROR_CATALOG "]"
 "[+NAME?getconf - get configuration values]"
 "[+DESCRIPTION?\bgetconf\b displays the system configuration value for"
@@ -52,7 +52,7 @@ static const char usage[] =
 "	\aname\a=\avalue\a form to the standard output, one per line."
 "	Only one of \b--call\b, \b--name\b or \b--standard\b may be specified.]"
 "[+?This implementation uses the \bastgetconf\b(3) string interface to the native"
-"	\bsysconf\b(2), \bconfstr\b(2), \bpathconf\b(2), and \bsysinfo\b(2)"
+"	\bsysconf\b(3), \bconfstr\b(3), \bpathconf\b(2), and \bsysinfo\b(2)"
 "	system calls."
 "	Invalid options and/or names not supported by \bastgetconf\b(3) cause"
 "	the default native \bgetconf\b, named by \b$(getconf GETCONF)\b, to"
@@ -63,9 +63,9 @@ static const char usage[] =
 "[b:base?List base variable name sans call and standard prefixes.]"
 "[c:call?Display variables with call prefix that matches \aRE\a. The call"
 "	prefixes are:]:[RE]{"
-"		[+CS?\bconfstr\b(2)]"
+"		[+CS?\bconfstr\b(3)]"
 "		[+PC?\bpathconf\b(2)]"
-"		[+SC?\bsysconf\b(2)]"
+"		[+SC?\bsysconf\b(3)]"
 "		[+SI?\bsysinfo\b(2)]"
 "		[+XX?Constant value.]"
 "}"
@@ -75,7 +75,7 @@ static const char usage[] =
 "[p:portable?Display the named \bwritable\b variables and values in a form that"
 "	can be directly executed by \bsh\b(1) to set the values. If \aname\a"
 "	is omitted then all \bwritable\b variables are listed.]"
-"[q:quote?\"...\" quote values.]"
+"[q:quote?\"...\" quote string values.]"
 "[r:readonly?Display the named \breadonly\b variables in \aname\a=\avalue\a form."
 "	If \aname\a is omitted then all \breadonly\b variables are listed.]"
 "[s:standard?Display variables with standard prefix that matches \aRE\a."
@@ -116,8 +116,8 @@ static const char usage[] =
             "is an implementation detail of process inheritance; it may "
             "change or vanish in the future; don't rely on it.]"
     "}"
-"[+SEE ALSO?\bpathchk\b(1), \bconfstr\b(2), \bpathconf\b(2),"
-"	\bsysconf\b(2), \bastgetconf\b(3)]"
+"[+SEE ALSO?\bpathchk\b(1), \bconfstr\b(3), \bpathconf\b(2),"
+"	\bsysconf\b(3), \bastgetconf\b(3)]"
 ;
 
 #include <cmd.h>

src/lib/libcmd/uname.c

@@ -66,7 +66,7 @@ static const char usage[] =
 "\n[ name ... ]\n"
 "\n"
 "[+SEE ALSO?\bhostname\b(1), \bgetconf\b(1), \buname\b(2),"
-"	\bsysconf\b(2), \bsysinfo\b(2)]"
+"	\bsysconf\b(3), \bsysinfo\b(2)]"
 ;
 
 #if defined(__STDPP__directive) && defined(__STDPP__hide)