GAS: Fix `abort' expansion in write.c

Remove an internal diagnostic regression introduced with the inclusion of
"libbfd.h" from write.c, added with:

commit e7ff5c732e7b95aafccd0910ea1a5cb8251a1033
Author: Alan Modra <amodra@gmail.com>
Date:   Fri Feb 16 03:40:17 2007 +0000

That change made "libbfd.h" override the `abort' definition provided by
"as.h" earlier on, making the message produced by any calls reached from
write.c, which is a part of the GAS proper, look like they came from
BFD, e.g.:

.../gas/testsuite/gas/elf/type.s: Assembler messages:
.../gas/testsuite/gas/elf/type.s:30: Error: symbol type "gnu_unique_object" is supported only by GNU targets
../as-new: BFD (GNU Binutils) 2.26.51.20160628 internal error, aborting at .../gas/write.c:608 in size_seg

../as-new: Please report this bug.

vs:

.../gas/testsuite/gas/elf/type.s: Assembler messages:
.../gas/testsuite/gas/elf/type.s:30: Error: symbol type "gnu_unique_object" is supported only by GNU targets
.../gas/testsuite/gas/elf/type.s: Internal error, aborting at .../gas/write.c:602 in size_seg
Please report this bug.

With the removal of "libbfd.h" restore the latter message format.

	gas/
	* write.c: Remove "libbfd.h" inclusion.

gas/ChangeLog

@@ -1,3 +1,7 @@
+2016-06-29  Maciej W. Rozycki  <macro@imgtec.com>
+
+	* write.c: Remove "libbfd.h" inclusion.
+
 2016-06-28  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* testsuite/gas/elf/elf.exp: Use `supports_gnu_unique' with the

gas/write.c

@@ -25,7 +25,6 @@
 #include "obstack.h"
 #include "output-file.h"
 #include "dwarf2dbg.h"
-#include "libbfd.h"
 #include "compress-debug.h"
 
 #ifndef TC_FORCE_RELOCATION