Fix single quotes in expansion operator string (re: 5ed9ffd6)

The referenced commit introduced the following bug:

> The closing quote does not appear to be registering during the
> parse of the following:
>
>	echo ${var:+'{}'}
>
> Within a script, this will result in:
>
>	syntax error at line 1: `'' unmatched

src/cmd/ksh93/data/lexstates.c,
src/cmd/ksh93/include/lexstates.h:
- Add new ST_MOD1 state table that is a copy of ST_QUOTE, but adds
  a special meaning (ST_LIT) for the single quote (position 39).

src/cmd/ksh93/sh/lex.c: sh_lex():
- For parameter expansion operators with old-style quoting
  (S_MOD1), use the new ST_MOD1 state table instead of ST_QUOTE.
  This causes single quotes within them to be processed properly.

src/cmd/ksh93/tests/quoting2.sh:
- Add tests.

Thanks to @gkamat for the bug report.
Resolves: https://github.com/ksh93/ksh/issues/290

src/cmd/ksh93/include/lexstates.h

@@ -79,7 +79,8 @@
 #define ST_DOLNAME	8
 #define ST_MACRO	9
 #define ST_QNEST	10
-#define ST_NONE		11
+#define ST_MOD1		11
+#define ST_NONE		12
 
 #include "FEATURE/locale"
 

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-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-04-26"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-04-30"	/* 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. */