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/cmd/ksh93/include/version.h

@@ -20,7 +20,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-04-16"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-04-20"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2021 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/tests/builtins.sh

@@ -22,8 +22,34 @@
 
 bincat=$(whence -p cat)
 
-# test shell builtin commands
+# ======
+# These are regression tests for the getconf builtin.
 builtin getconf
+bingetconf=$(getconf GETCONF)
+bad_result=$(getconf --version 2>&1)
+
+# The -l option should convert all variable names to lowercase.
+# https://github.com/att/ast/issues/1171
+got=$(getconf -l | awk '{ gsub(/=.*/, "") } /[[:upper:]]/ { print }')
+[[ -n $got ]] && err_exit "'getconf -l' doesn't convert all variable names to lowercase" \
+	"(got $(printf %q "$got"))"
+
+# The -q option should quote all string values.
+# https://github.com/att/ast/issues/1173
+exp="GETCONF=\"$bingetconf\""
+got=$(getconf -q | grep 'GETCONF=')
+[[ $exp == "$got" ]] || err_exit "'getconf -q' fails to quote string values" \
+	"(expected $exp, got $got)"
+
+# The -n option should only return matching names.
+# https://github.com/ksh93/ksh/issues/279
+exp="GETCONF=$bingetconf"
+got=$(getconf -n GETCONF)
+[[ $exp == "$got" ]] || err_exit "'getconf -n' doesn't match names correctly" \
+	"(expected $exp, got $got)"
+
+# ======
+# Test shell builtin commands
 : ${foo=bar} || err_exit ": failed"
 [[ $foo == bar ]] || err_exit ": side effects failed"
 set -- - foobar