lex.c: prevent restoring outdated stack pointer

Lexical levels are stored in a dynamically grown array of int values
grown by the stack_grow function. The pointer lex_match and the
maximum index lex_max are part of the lexer state struct that is now
saved and restored in various places -- see e.g. 37044047, a2bc49be.
If the stack needs to be grown, it is reallocated in stack_grow()
using sh_realloc(). If that happens between saving and restoring the
lexer state, then an outdated pointer is restored, and crash.

src/cmd/ksh93/include/shlex.h,
src/cmd/ksh93/sh/lex.c:
- Take lex_match and lex_max out of the lexer state struct and make
  them separate static variables.

src/cmd/ksh93/edit/edit.c:
- While we're at it, save and restore the lexer state in a way that
  is saner than the 93v- beta approach (re: 37044047) as well as
  more readable. Instead of permanently allocating memory, use a
  local variable to save the struct. Save/restore directly around
  the sh_trap() call that actually needs this done.

Resolves: https://github.com/ksh93/ksh/issues/482

src/cmd/ksh93/include/shlex.h

@@ -61,8 +61,6 @@ struct _shlex_pvt_lexdata_
 	char 		*first;
 	int		level;
 	int		lastc;
-	int		lex_max;
-	int		*lex_match;
 	int		lex_state;
 	int		docextra;
 #if SHOPT_KIA