Change gdbsupport not to rely on BFD

This changes gdbsupport so that it no longer relies on BFD.  This is a
precursor to making gdbserver use the already-built gdbsupport,
because building gdbserver should not require BFD to be built.

The most notable change here is that CORE_ADDR is always a 64-bit
type.  This makes it so that gdb acts as if it were always built in
64-bit mode.

ChangeLog
2020-03-12  Tom Tromey  <tom@tromey.com>

	* Makefile.in: Rebuild.
	* Makefile.def (gdbsupport): Don't depend on bfd.

gdbsupport/ChangeLog
2020-03-12  Tom Tromey  <tom@tromey.com>

	* common-types.h: Remove GDBSERVER code.
	(gdb_byte, CORE_ADDR, LONGEST, ULONGEST): Redefine.
	* common-defs.h: Remove GDBSERVER code.