When checking for the location of the sigcontext struct it is not taken into
account that a different libc than glibc could be used. It falls back to libc5
which leads to a sigcontext redefinition error when using the musl libc. The
patch simply removes the misleading checks since we're way beyond those
versions anyway.

--- libguile/gc_os_dep.c.orig	2010-12-13 18:25:01.000000000 +0100
+++ libguile/gc_os_dep.c	2017-09-17 23:01:55.494204333 +0200
@@ -1445,40 +1445,6 @@
 				/* include assembly code to do it well.	*/
 # endif
 
-# if defined(LINUX) && !defined(POWERPC)
-
-# if 0
-#   include <linux/version.h>
-#   if (LINUX_VERSION_CODE <= 0x10400)
-      /* Ugly hack to get struct sigcontext_struct definition.  Required  */
-      /* for some early 1.3.X releases.  Will hopefully go away soon. */
-      /* in some later Linux releases, asm/sigcontext.h may have to   */
-      /* be included instead.                                         */
-#     define __KERNEL__
-#     include <asm/signal.h>
-#     undef __KERNEL__
-#  endif
-
-#  else
-
-      /* Kernels prior to 2.1.1 defined struct sigcontext_struct instead of */
-      /* struct sigcontext.  libc6 (glibc2) uses "struct sigcontext" in     */
-      /* prototypes, so we have to include the top-level sigcontext.h to    */
-      /* make sure the former gets defined to be the latter if appropriate. */
-#     include <features.h>
-#     if 2 <= __GLIBC__
-#       if 2 == __GLIBC__ && 0 == __GLIBC_MINOR__
-	  /* glibc 2.1 no longer has sigcontext.h.  But signal.h	*/
-	  /* has the right declaration for glibc 2.1.			*/
-#         include <sigcontext.h>
-#       endif /* 0 == __GLIBC_MINOR__ */
-#     else /* not 2 <= __GLIBC__ */
-        /* libc5 doesn't have <sigcontext.h>: go directly with the kernel   */
-        /* one.  Check LINUX_VERSION_CODE to see which we should reference. */
-#       include <asm/sigcontext.h>
-#     endif /* 2 <= __GLIBC__ */
-#   endif
-# endif
 # if !defined(OS2) && !defined(PCR) && !defined(AMIGA) && !defined(MACOS)
 #   include <sys/types.h>
 #   if !defined(MSWIN32) && !defined(SUNOS4)