elfutils: Fix port build after recent basename() API break

The previous basename() API was shadowing bugs anyway.  This Linux-originated
library assumes GNU basename(3) behavior.  GNU basename(3) is non-destructive
and non-allocating; it always returns a pointer into the original string.  This
library uses that behavior to do things like compare pointer results directly
(the source path was already a basename) or subtract pointer values directly
(compute the substring that constitutes dirname).

Resolve the issue by aliasing all internal elfutils basename() invocations
through an implementation of GNU basename(3) named "eu_basename."

Build log highlighting the problem:
http://beefy4.nyi.freebsd.org/data/head-amd64-default/p419462_s303652/logs/elfutils-0.163_6.log

Approved by:	bdrewery
Differential Revision:	https://reviews.freebsd.org/D7404

devel/elfutils/Makefile

@@ -3,7 +3,7 @@
 
 PORTNAME=	elfutils
 PORTVERSION=	0.163
-PORTREVISION=	6
+PORTREVISION=	7
 CATEGORIES=	devel
 MASTER_SITES=	https://fedorahosted.org/releases/e/l/elfutils/${PORTVERSION}/
 

devel/elfutils/files/patch-lib_eu-config.h

@@ -1,6 +1,6 @@
 --- lib/eu-config.h.orig	2015-06-11 11:38:55 UTC
 +++ lib/eu-config.h
-@@ -187,4 +187,147 @@ asm (".section predict_data, \"aw\"; .pr
+@@ -187,4 +187,167 @@ asm (".section predict_data, \"aw\"; .pr
  #endif
  
  
@@ -57,6 +57,26 @@
 +	return (realpath(path, NULL));
 +}
 +
++/*
++ * A GNU-like basename().
++ *
++ * Unlike POSIX basename(3), this version never modifies its argument.  If the
++ * argument ends in a slash, it returns the empty string.
++ */
++static inline char *
++eu_basename(const char *path)
++{
++	const char *slash;
++
++	slash = strrchr(path, '/');
++	if (slash != NULL)
++		slash++;
++	else
++		slash = path;
++	return (__DECONST(char *, slash));
++}
++#define	basename	eu_basename
++
 +#ifndef	TEMP_FAILURE_RETRY
 +#define	TEMP_FAILURE_RETRY(expr)	({		\
 +	long value;					\