libgo: Use MAP_FIXED if necessary to grab arena.

From Rainer Orth.

	PR go/48240
	* configure.ac: Check for mincore.
	* configure: Regenerate.
	* config.h.in: Regenerate.
	* runtime/mem.c: Include unistd.h.
	(addrspace_free): New function.
	(runtime_SysMap): Retry 64-bit runtime_mmap with MAP_FIXED.

From-SVN: r171961
diff --git a/libgo/configure.ac b/libgo/configure.ac
index 77b9f94..e772c2a 100644
--- a/libgo/configure.ac
+++ b/libgo/configure.ac
@@ -426,7 +426,7 @@
 AC_CHECK_HEADERS(sys/mman.h syscall.h sys/epoll.h sys/ptrace.h sys/syscall.h sys/user.h sys/utsname.h sys/select.h)
 AM_CONDITIONAL(HAVE_SYS_MMAN_H, test "$ac_cv_header_sys_mman_h" = yes)
 
-AC_CHECK_FUNCS(srandom random strerror_r strsignal wait4)
+AC_CHECK_FUNCS(srandom random strerror_r strsignal wait4 mincore)
 AM_CONDITIONAL(HAVE_STRERROR_R, test "$ac_cv_func_strerror_r" = yes)
 AM_CONDITIONAL(HAVE_WAIT4, test "$ac_cv_func_wait4" = yes)