gcc: Add clang's -Wno-c++11-narrowing where we have gcc's -Wno-narrowing.This fixes some clang buildworld issues.Not sure why it errors without this flag even though no -Werror is set.
Adjust makefiles for GCC80 update.
gcc80: Partially implement TOOLCHAIN_CHECKING.Will be needed for special feature testing in newer binutils.
gcc80: Mark few sources as special for narrowing.While there, add -Wpragmas suppression for gcc47.
gcc80: Bring in makefiles but leave them unhooked.Makefile infrastructure was reused from gcc50 one writen by John Marino.