LibC: Stub out fmemopen()

Userland/Libraries/LibC/stdio.cpp

@@ -1067,6 +1067,13 @@ FILE* fdopen(int fd, const char* mode)
     return FILE::create(fd, flags);
 }
 
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html
+FILE* fmemopen(void*, size_t, const char*)
+{
+    // FIXME: Implement me :^)
+    TODO();
+}
+
 static inline bool is_default_stream(FILE* stream)
 {
     return stream == stdin || stream == stdout || stream == stderr;

Userland/Libraries/LibC/stdio.h

@@ -57,6 +57,7 @@ int remove(const char* pathname);
 FILE* fdopen(int fd, const char* mode);
 FILE* fopen(const char* pathname, const char* mode);
 FILE* freopen(const char* pathname, const char* mode, FILE*);
+FILE* fmemopen(void* buf, size_t size, const char* mode);
 void flockfile(FILE* filehandle);
 void funlockfile(FILE* filehandle);
 int fclose(FILE*);