Use genversion to generate version.h.

c++tools/ChangeLog:

	* Makefile.in: Include also ../gcc folder.

gcc/ChangeLog:

	* Makefile.in: Rename gcov-iov to genversion and depend
	on version.h (instead of gcov-iov.h).
	* gcov-io.h: Include version.h instread of gcov-iov.h.
	* gengtype-state.c (read_state_version): Likewise.
	* gcov-iov.c: Moved to...
	* genversion.c: ...here.
	* lto-streamer.h (LTO_major_version): Define it with
	GCC_major_version.
	* version.c: Removed.
	* version.h: Removed.

libgcc/ChangeLog:

	* libgcov-driver.c (gcov_version): Use different name that does
	not clash with newly introduced macro.