libast: optget(3): Fix memory leak in --help/--man info

src/lib/libast/misc/optget.c: textout(): case ']':
- Before returning, call pop() to free any \f...\f info items that
  are left. Note that this is a safe no-op if the pointer is null.

Resolves: https://github.com/ksh93/ksh/issues/407
Co-authored-by: Martijn Dekker <martijn@inlv.org>

NEWS

@@ -7,6 +7,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
 
 - Fixed another corner case bug in the 'test'/'[' command.
 
+- A memory leak was fixed in the --man self-documentation options
+  of built-in commands.
+
 2022-03-05:
 
 - The 'enum' command can now create more than one type per invocation.

src/cmd/ksh93/tests/leaks.sh

@@ -418,7 +418,7 @@ DO
 DONE
 
 # ======
-TEST title='showing --man info' known=y url=https://github.com/ksh93/ksh/issues/407
+TEST title='showing --man info'
 DO
 	set --man 2>/dev/null
 	ulimit --man 2>/dev/null

src/lib/libast/misc/optget.c

@@ -2157,6 +2157,7 @@ textout(Sfio_t* sp, register char* s, char* conform, int conformlen, int style,
 								break;
 						}
 					}
+					pop(psp);
 					return s;
 				}
 				s++;