INIT/cc.darwin: re-suppress redefined macro warnings (re: a1d8ff6f)

Allowing redefined macro warnings was not such a good idea, as the
Apple compiler flags redefine the _ast_int8_t macro right on the
command line, producing a warning for every cc invocation.

(cherry picked from commit 929930224f898cb1371471fe554fabb73b31d11f)

TODO

@@ -1,5 +1,20 @@
 TODO for AT&T ksh93, 93u+m bugfix branch
 
+______
+Fix regression test failures:
+
+- On OpenBSD, there are 15 locale-related test failures in variables.sh.
+
+______
+Fix build failures:
+
+- ksh does not currently build on AIX, HP-UX, Solaris, or QNX.
+
+______
+Remove hack for 'test -t' with no args == 'test -t 1':
+- from sh/parse.c, qscan()
+- from bltins/test.c
+
 ______
 Fix or remove broken default aliases:
 
@@ -38,6 +53,7 @@ https://github.com/modernish/modernish/tree/0.16/lib/modernish/cap/
   or
 	set -- command ls; "$@"
   don't work.
+  See also: https://github.com/att/ast/issues/963
 
 - BUG_CMDSPASGN: preceding a "special builtin"[*] with 'command' does not
   stop preceding invocation-local variable assignments from becoming global.

src/cmd/INIT/cc.darwin

@@ -46,7 +46,7 @@ init)	echo "cc: arguments expected" >&2
 cpp)	$CC -E "$@"
 	;;
 cc)	$CC -DSHOPT_SPAWN=0 -D_ast_int8_t=int64_t -D_lib_memccpy \
-		-Wno-unused-value -Wno-parentheses "$@"
+		-Wno-unused-value -Wno-parentheses -Wno-macro-redefined "$@"
 	;;
 dll)	$CC -Wl,-flat_namespace -dynamiclib -undefined dynamic_lookup "$@"
 	;;