Changes to support GDB running on DOS using GO32 and H8 support

	Changes to support GDB running on DOS using GO32 and H8 support

	* defs.h: if xm.h doesn't define FOPEN_RB, include "fopen-same.h",
	allowing hosts with different text and binary file formats to
	work.
	* coffread.c (read_coff_symtab): changed calling convention and
	operation - now it opens its own file with FOPEN_RB rather than
	duping and fdopening the provided handle.
	* dbxread.c, cplus-dem.c: #include mangling.
	* exec.c: If O_BINARY isn't defined, set it to 0, call openp for
	binary files oring in the right bit.
	* utils.c, terminal.h, inflow.c: hackery because dos doesn't have terminals.
	* remote-hms.c: cleanup to use the new remote serial stuff
	* serial.h, ser-termios.c, ser-go32.c: newfiles to provide host
	independent remote terminal I/O.
	* remote.c: if DONT_USE_REMOTE is defined, then don't use it.
	* source.c (openp): fix off by one problem removing / - can now
	open a source file in the root directory with DOS.
	* values.c (value_as_pointer): remove bogus address bits from
	long. (unpack_long): unpack into unsigned long/short if pointer.
sun4.mh: use the ser-termios stuff
go32.mh: use the ser-go32 stuff