fix the mremap signature

The mremap definition was incorrect (unsigned long instead of int) and
it was missing the optional new_address parameter.

Change-Id: Ib9d0675aaa098c21617cedc9b2b8cf267be3aec4
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 4188c15..526b6d0 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -107,7 +107,7 @@
 int         ___close:close(int)  all
 pid_t       __getpid:getpid()  all
 int         munmap(void*, size_t)  all
-void*       mremap(void*, size_t, size_t, unsigned long)  all
+void*       ___mremap:mremap(void*, size_t, size_t, int, void*)  all
 int         msync(const void*, size_t, int)    all
 int         mprotect(const void*, size_t, int)  all
 int         madvise(void*, size_t, int)  all