bfd: Rename read_{signed,unsigned}_leb128, safe_read_leb128

bfd: Rename read_{signed,unsigned}_leb128, safe_read_leb128

Give these bfd-internal symbols with external linkage a _bfd_ prefix
to avoid collisions in the global symbol namespace.

bfd/ChangeLog:
2017-02-17  Pedro Alves  <palves@redhat.com>

	* dwarf2.c, elf-attrs.c, elf32-nds32.c: Adjust all callers.
	* libbfd.c (read_unsigned_leb128): Rename to ...
	(_bfd_read_unsigned_leb128): ... this.
	(read_signed_leb128): Rename to ...
	(_bfd_read_signed_leb128): ... this.
	(safe_read_leb128): Rename to ...
	(_bfd_safe_read_leb128): ... this.
	* libbfd-in.h (read_unsigned_leb128): Rename to ...
	(_bfd_read_unsigned_leb128): ... this.
	(read_signed_leb128): Rename to ...
	(_bfd_read_signed_leb128): ... this.
	(safe_read_leb128): Rename to ...
	(_bfd_safe_read_leb128): ... this.
	* libbfd.h: Renegerate.