Remove ctype compat macros. NFC (#20960)

libcxx has direct support for `_NEWLIB_VERSION` in `__locale` so just
use that.  This libcxx support was added in http://reviews.llvm.org/D7888
and landed in emscripten in #13154.

Author: sbc100

system/include/compat/ctype.h

@@ -406,12 +406,12 @@ public:
     static const mask __regex_word = 0x4000; // 0x8000 and 0x0100 and 0x00ff are used
 # define _LIBCPP_CTYPE_MASK_IS_COMPOSITE_PRINT
 # define _LIBCPP_CTYPE_MASK_IS_COMPOSITE_ALPHA
-#elif defined(__APPLE__) || defined(__FreeBSD__) || defined(__EMSCRIPTEN__) || defined(__NetBSD__)
+#elif defined(__APPLE__) || defined(__FreeBSD__) || defined(__NetBSD__)
 # ifdef __APPLE__
     typedef __uint32_t mask;
 # elif defined(__FreeBSD__)
     typedef unsigned long mask;
-# elif defined(__EMSCRIPTEN__) || defined(__NetBSD__)
+# elif defined(__NetBSD__)
     typedef unsigned short mask;
 # endif
     static const mask space  = _CTYPE_S;