Don't issue errors on GDB Python files

Don't issue errors on GDB Python files

Many packages, including GCC, install Python files for GDB in library
diretory. ldconfig reads them and issue errors since they aren't ELF
files:

ldconfig: /usr/gcc-5.1.1/lib/libstdc++.so.6.0.21-gdb.py is not an ELF file - it has the wrong magic bytes at the start.

ldconfig: /usr/gcc-5.1.1/libx32/libstdc++.so.6.0.21-gdb.py is not an ELF file - it has the wrong magic bytes at the start.

ldconfig: /usr/gcc-5.1.1/lib64/libstdc++.so.6.0.21-gdb.py is not an ELF file - it has the wrong magic bytes at the start.

This patch silences ldconfig on GDB Python files by checking filenames
with -gdb.py suffix.

	[BZ #18585]
	* elf/readlib.c (is_gdb_python_file): New.
	(process_file): Don't issue errors on filenames with -gdb.py
	suffix.