remove hidden-visibility.h

I am removing this on the advice of a member of the Gentoo toolchain
team. It was explained to me that this doesn't offer any significant
benefits to OpenRC.

If anyone ffeels differently, please open a pull request reverting
this and adding an explanation of what it does and how to know which
functions to mark hidden in the future.

This fixes #301.

src/includes/hidden-visibility.h

@@ -1,26 +0,0 @@
-/*
- * Written by Mike Frysinger
- * Placed in the Public Domain
- */
-
-#ifndef _HIDDEN_VISIBILITY_H_
-#define _HIDDEN_VISIBILITY_H_
-
-#if defined(__ELF__) && defined(__GNUC__)
-# define __hidden_asmname(name) __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
-# define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
-# define __hidden_asmname2(prefix, name) #prefix name
-# define __hidden_proto(name, internal) \
-	extern __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
-	__attribute__ ((visibility ("hidden")));
-# define __hidden_ver(local, internal, name) \
-   extern __typeof (name) __EI_##name __asm__(__hidden_asmname (#internal)); \
-   extern __typeof (name) __EI_##name __attribute__((alias (__hidden_asmname1 (,#local))))
-# define hidden_proto(name) __hidden_proto(name, __RC_##name)
-# define hidden_def(name) __hidden_ver(__RC_##name, name, name);
-#else
-# define hidden_proto(name)
-# define hidden_def(name)
-#endif
-
-#endif