Add a "fork" of musl as //fusl.

fusl/include/ctype.h

+#ifndef _CTYPE_H
+#define _CTYPE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <features.h>
+
+int   isalnum(int);
+int   isalpha(int);
+int   isblank(int);
+int   iscntrl(int);
+int   isdigit(int);
+int   isgraph(int);
+int   islower(int);
+int   isprint(int);
+int   ispunct(int);
+int   isspace(int);
+int   isupper(int);
+int   isxdigit(int);
+int   tolower(int);
+int   toupper(int);
+
+#ifndef __cplusplus
+static __inline int __isspace(int _c)
+{
+        return _c == ' ' || (unsigned)_c-'\t' < 5;
+}
+
+#define isalpha(a) (0 ? isalpha(a) : (((unsigned)(a)|32)-'a') < 26)
+#define isdigit(a) (0 ? isdigit(a) : ((unsigned)(a)-'0') < 10)
+#define islower(a) (0 ? islower(a) : ((unsigned)(a)-'a') < 26)
+#define isupper(a) (0 ? isupper(a) : ((unsigned)(a)-'A') < 26)
+#define isprint(a) (0 ? isprint(a) : ((unsigned)(a)-0x20) < 0x5f)
+#define isgraph(a) (0 ? isgraph(a) : ((unsigned)(a)-0x21) < 0x5e)
+#define isspace(a) __isspace(a)
+#endif
+
+
+#if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
+ || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \
+ || defined(_BSD_SOURCE)
+
+#define __NEED_locale_t
+#include <bits/alltypes.h>
+
+int   isalnum_l(int, locale_t);
+int   isalpha_l(int, locale_t);
+int   isblank_l(int, locale_t);
+int   iscntrl_l(int, locale_t);
+int   isdigit_l(int, locale_t);
+int   isgraph_l(int, locale_t);
+int   islower_l(int, locale_t);
+int   isprint_l(int, locale_t);
+int   ispunct_l(int, locale_t);
+int   isspace_l(int, locale_t);
+int   isupper_l(int, locale_t);
+int   isxdigit_l(int, locale_t);
+int   tolower_l(int, locale_t);
+int   toupper_l(int, locale_t);
+
+int   isascii(int);
+int   toascii(int);
+#define _tolower(a) ((a)|0x20)
+#define _toupper(a) ((a)&0x5f)
+#define isascii(a) (0 ? isascii(a) : (unsigned)(a) < 128)
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif