Support (add machine description for) TILE-Gx and TILEPro targets

Support (add machine description for) TILE-Gx and TILEPro targets

This patch is an updated version of the CentOS 6 patch that we have
been carrying as part of our own CentOS-like distribution since 2012.

* include/private/gcconfig.h (TILEGX, TILEPRO) [__tile__]: New macro.
* include/private/gcconfig.h (mach_type_known, CPP_WORDSZ, MACH_TYPE,
ALIGNMENT, ALIGN_DOUBLE, PREFETCH, CACHE_LINE_SIZE,
USE_GENERIC_PUSH_REGS, OS_TYPE, __data_start, DATASTART,
LINUX_STACKBOTTOM, DYNAMIC_LOADING, ALIGNMENT): Define for TILEGX and
TILEPRO.