Better handling of platforms which hide "extended" functionality

Some platforms apparently feel -std=c99, which defines
__STRICT_ANSI__, should also hide a bunch of function prototypes.
This rather sucks.  At least try to deal with it.

MinGW and DJGPP both have this problem, in particular.

compiler.h

@@ -24,11 +24,6 @@
 # include "config.h"
 #endif
 
-/* __STRICT_ANSI__ buggers up MinGW, so disable it */
-#ifdef __MINGW32__
-# undef __STRICT_ANSI__
-#endif
-
 /* This is required to get the standard <inttypes.h> macros when compiling
    with a C++ compiler.  This must be defined *before* <inttypes.h> is
    included, directly or indirectly. */
@@ -80,4 +75,25 @@ typedef enum { false, true } bool;
 # endif
 #endif
 
+/* Some misguided platforms hide the defs for these */
+#if defined(HAVE_STRCASECMP) && !HAVE_DECL_STRCASECMP
+int strcasecmp(const char *, const char *);
+#endif
+
+#if defined(HAVE_STRICMP) && !HAVE_DECL_STRICMP
+int stricmp(const char *, const char *);
+#endif
+
+#if defined(HAVE_STRNCASECMP) && !HAVE_DECL_STRNCASECMP
+int strncasecmp(const char *, const char *, size_t);
+#endif
+
+#if defined(HAVE_STRNICMP) && !HAVE_DECL_STRNICMP
+int strnicmp(const char *, const char *, size_t);
+#endif
+
+#if defined(HAVE_STRSEP) && !HAVE_DECL_STRSEP
+char *strsep(char **, const char *);
+#endif
+
 #endif	/* NASM_COMPILER_H */

configure.in

@@ -124,6 +124,15 @@ AC_CHECK_FUNCS(strsep)
 AC_CHECK_FUNCS(getuid)
 AC_CHECK_FUNCS(getgid)
 
+dnl Check for functions that might not be declared in the headers for
+dnl various idiotic reasons (mostly because of library authors
+dnl abusing the meaning of __STRICT_ANSI__)
+AC_CHECK_DECLS(strcasecmp)
+AC_CHECK_DECLS(stricmp)
+AC_CHECK_DECLS(strncasecmp)
+AC_CHECK_DECLS(strnicmp)
+AC_CHECK_DECLS(strsep)
+
 if test $ac_cv_prog_make_vpathok = no; then
   echo Copying generated srcs into build directory to compensate for VPATH breakage
   for file in macros.c insnsa.c insnsd.c insnsn.c insnsi.h version.h version.mac; do