Hook gcc 3.4 into the buildworld. Rearrange HOST_CCVER so it becomes the

Hook gcc 3.4 into the buildworld.  Rearrange HOST_CCVER so it becomes the
responsibility of the Makefile element that is overriding CCVER.  Get rid
of the obsolete MY_CCVER magic.  Fix improper use of ${.TARGET} in
cc34/cc_tools/Makefile.tools.  Do not try to override _CPUCFLAGS in
bsd.hostprog.mk, which doesn't handle the generic .nx/.no case.  Instead
remove -mtune, -mcpu, and -march options in NXCFLAGS and NXCXXFLAGS.

Work-by: Joerg Sonnenberger <joerg@crater.dragonflybsd.org>
Reviewed-by: Matthew Dillon <dillon@backplane.com>