Fix [ \( str -a str \) ], [ \( str -o str \) ]

Symptoms:

$ test \( string1 -a string2 \)
/usr/local/bin/ksh: test: argument expected
$ test \( string1 -o string2 \)
/usr/local/bin/ksh: test: argument expected

The parentheses should be irrelevant and this should be a test for
the non-emptiness of string1 and/or string2.

src/cmd/ksh93/bltins/test.c:

- b_test(): There is a block where the case of 'test' with five or
  less arguments, the first and last one being parentheses, is
  special-cased. The parentheses are removed as a workaround: argv
  is increased to skip the opening parenthesis and argc is
  decreased by 2. However, there is no corresponding increase of
  tdata.av which is a copy of this function's argv. This renders
  the workaround ineffective. The fix is to add that increase.

- e3(): Do not handle '!' as a negator if not followed by an
  argument. This allows a right-hand expression that is equal to
  '!' (i.e. a test for the non-emptiness of the string '!').

NEWS

@@ -3,6 +3,11 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2021-11-14:
+
+- Another test/[ fix: "test \( string1 -a string2 \)" and "test \( string1 -o
+  string2 \)" no longer give an incorrect "argument expected" error message.
+
 2021-11-13:
 
 - The test/[ built-in command now supports the '<' and '=~' operators from [[.