Fix compiler warnings and regression test failure (re: fc2d5a6)

src/cmd/ksh93/bltins/test.c:
- Fix the following compiler warnings from clang:
  test.c:554:11: warning: assigning to 'char *' from 'const char []'
  discards qualifiers
  [-Wincompatible-pointer-types-discards-qualifiers]
                                e_msg = e_badop;
                                      ^ ~~~~~~~
  test.c:556:11: warning: assigning to 'char *' from 'const char []'
  discards qualifiers
  [-Wincompatible-pointer-types-discards-qualifiers]
                                e_msg = e_unsupported_op;
                                      ^ ~~~~~~~~~~~~~~~~
  test.c:560:1: warning: control may reach end of non-void function
  [-Wreturn-type]

src/cmd/ksh93/tests/builtins.sh:
- Fix regression test by updating error message text.

src/cmd/ksh93/bltins/test.c

@@ -547,16 +547,13 @@ int test_binop(Shell_t *shp,register int op,const char *left,const char *right)
 		{
 			/* fallback for operators not supported by the test builtin */
 			int i=0;
-			char *e_msg;
 			while(shtab_testops[i].sh_number && shtab_testops[i].sh_number != op)
 				i++;
-			if(op==TEST_END)
-				e_msg = e_badop;
-			else
-				e_msg = e_unsupported_op;
-			errormsg(SH_DICT,ERROR_exit(2),e_msg,shtab_testops[i].sh_name);
+			errormsg(SH_DICT, ERROR_exit(2), op==TEST_END ? e_badop : e_unsupported_op, shtab_testops[i].sh_name);
 		}
 	}
+	/* NOTREACHED */
+	return(0);
 }
 
 /*

src/cmd/ksh93/tests/builtins.sh

@@ -1002,13 +1002,13 @@ fi
 actual=$($SHELL -c 'test foo =~ foo' 2>&1)
 actual_status=$?
 actual=${actual#*: }
-expect='test: =~: operator not supported; use [[...]]'
+expect='test: =~: operator not supported; use [[ ... ]]'
 expect_status=2
 [[ "$actual" = "$expect" ]] || err_exit "test =~ failed (expected $expect, got $actual)"
 [[ "$actual_status" = "$expect_status" ]] ||
     err_exit "test =~ failed with the wrong exit status (expected $expect_status, got $actual_status)"
 
-# Invalid operators 'test' and '[[...]]' both reject should also cause an error with exit status 2.
+# Invalid operators 'test' and '[[ ... ]]' both reject should also cause an error with exit status 2.
 for operator in '===' ']]'
 do
 	actual="$($SHELL -c "test foo $operator foo" 2>&1)"