gdbsupport: make use of safe-ctype functions from libiberty

gdbsupport: make use of safe-ctype functions from libiberty

Make use of the safe-ctype replacements for the standard ctype
character checking functions in gdbsupport/common-utils.cc.  The
gdbsupport library is included into both gdb and gdbserver, and on the
gdbserver side there are two targets, gdbserver itself, and also
libinproctrace.so.

libiberty was already being included in the gdbserver link command,
but was missing from the libinproctrace.so link.  As a result, after
changing gdbsupport/common-utils.cc to depend on libiberty,
libinproctrace.so would no longer link until I modified its link line.

gdbserver/ChangeLog:

	* Makefile.in (IPA_LIB): Include libiberty library.

gdbsupport/ChangeLog:

	* gdbsupport/common-utils.cc: Change 'ctype.h' include to
	'safe-ctype.h'.
	(extract_string_maybe_quoted): Use safe-ctype function versions.
	(is_digit_in_base): Likewise.
	(digit_to_int): Likewise.
	(strtoulst): Likewise.
	(skip_spaces): Likewise.
	(skip_to_space): Likewise.