Fix regex_traits<T>::char_class_type for Android.

Android can't use ctype_base::mask for its char_class_type because the
bionic ctype implementation comes from openbsd, which uses an 8-bit
ctype mask which isn't large enough to encode the standard ctypes and
__regex_word.

Change-Id: Iee4b8dd465ff2cb358ed2b10e1c3a499437403b7

include/regex

@@ -962,9 +962,18 @@ public:
     typedef _CharT                  char_type;
     typedef basic_string<char_type> string_type;
     typedef locale                  locale_type;
+#ifdef __ANDROID__
+    typedef uint16_t                char_class_type;
+#else
     typedef ctype_base::mask        char_class_type;
+#endif
 
+#ifdef __ANDROID__
+    static const char_class_type __regex_word = 0x8000;
+#else
     static const char_class_type __regex_word = 0x80;
+#endif
+
 private:
     locale __loc_;
     const ctype<char_type>* __ct_;