silence macro redefinition warnings (re: 7003aba4)

src/cmd/ksh93/bltins/test.c,
src/cmd/ksh93/sh/arith.c,
src/cmd/ksh93/sh/streval.c:
- #undef ERROR_exit before redefining it, so clang stops nagging.

src/cmd/ksh93/bltins/test.c

@@ -97,6 +97,7 @@ int _ERROR_exit_b_test(int exitval)
 	}
 	return(ERROR_exit(exitval));
 }
+#undef ERROR_exit
 #define ERROR_exit(n) _ERROR_exit_b_test(n)
 
 static int test_strmatch(Shell_t *shp,const char *str, const char *pat)

src/cmd/ksh93/sh/arith.c

@@ -32,6 +32,7 @@
 #include	"builtins.h"
 
 /* POSIX requires error status > 1 if called from test builtin */
+#undef ERROR_exit
 #define ERROR_exit(n) _ERROR_exit_b_test(n)
 
 #ifndef LLONG_MAX

src/cmd/ksh93/sh/streval.c

@@ -37,6 +37,7 @@
 #include	"defs.h"	/* for sh.decomma */
 
 /* POSIX requires error status > 1 if called from test builtin */
+#undef ERROR_exit
 #define ERROR_exit(n) _ERROR_exit_b_test(n)
 
 #ifndef ERROR_dictionary