d: Remove D-specific version definitions from target headers

This splits up the targetdm sources so that each file only handles one
target platform.

Having all logic kept in the headers means that they could become out of
sync when a new target is added (loongarch*-*-linux*) or accidentally
broken if some headers in tm_file are changed about.

gcc/ChangeLog:

	* config.gcc: Split out glibc-d.o into linux-d.o, kfreebsd-d.o,
	kopensolaris-d.o, and gnu-d.o.  Split out cygwin-d.o from winnt-d.o.
	* config/arm/linux-eabi.h (EXTRA_TARGET_D_OS_VERSIONS): Remove.
	* config/gnu.h (GNU_USER_TARGET_D_OS_VERSIONS): Remove.
	* config/i386/cygwin.h (EXTRA_TARGET_D_OS_VERSIONS): Remove.
	* config/i386/linux-common.h (EXTRA_TARGET_D_OS_VERSIONS): Remove.
	* config/i386/mingw32.h (EXTRA_TARGET_D_OS_VERSIONS): Remove.
	* config/i386/t-cygming: Add cygwin-d.o.
	* config/i386/winnt-d.cc (winnt_d_os_builtins): Only add
	MinGW-specific version condition.
	* config/kfreebsd-gnu.h (GNU_USER_TARGET_D_OS_VERSIONS): Remove.
	* config/kopensolaris-gnu.h (GNU_USER_TARGET_D_OS_VERSIONS): Remove.
	* config/linux-android.h (ANDROID_TARGET_D_OS_VERSIONS): Remove.
	* config/linux.h (GNU_USER_TARGET_D_OS_VERSIONS): Remove.
	* config/mips/linux-common.h (EXTRA_TARGET_D_OS_VERSIONS): Remove.
	* config/t-glibc: Remove glibc-d.o, add gnu-d.o, kfreebsd-d.o,
	kopensolaris-d.o.
	* config/t-linux: Add linux-d.o.
	* config/glibc-d.cc: Remove file.
	* config/gnu-d.cc: New file.
	* config/i386/cygwin-d.cc: New file.
	* config/kfreebsd-d.cc: New file.
	* config/kopensolaris-d.cc: New file.
	* config/linux-d.cc: New file.