This removes support for EOL versions of NetBSD and syncs the
definitions with patches from NetBSD upstream.

The only change here that isn't from upstream is to use _CTYPE_BL for
the isblank class, which is correct but wasn't previously done either in
FSF GCC or the NetBSD packages.

2020-01-16  Kai-Uwe Eckhardt  <kuehro@gmx.de>
	    Matthew Bauer  <mjbauer95@gmail.com>
	    Jonathan Wakely  <jwakely@redhat.com>

	PR bootstrap/64271 (partial)
	* config/os/bsd/netbsd/ctype_base.h (ctype_base::mask): Change type
	to unsigned short.
	(ctype_base::alpha, ctype_base::digit, ctype_base::xdigit)
	(ctype_base::print, ctype_base::graph, ctype_base::alnum): Sync
	definitions with NetBSD upstream.
	(ctype_base::blank): Use _CTYPE_BL.
	* config/os/bsd/netbsd/ctype_configure_char.cc (_C_ctype_): Remove
	Declaration.
	(ctype<char>::classic_table): Use _C_ctype_tab_ instead of _C_ctype_.
	(ctype<char>::do_toupper, ctype<char>::do_tolower): Cast char
	parameters to unsigned char.
	* config/os/bsd/netbsd/ctype_inline.h (ctype<char>::is): Likewise.