Use `=' rather than `:=' when setting up CC, so that `gcc' can be

Use `=' rather than `:=' when setting up CC, so that `gcc' can be
defined as a foreign command if necessary; eliminate `set
symbol/scope=noGlobal' for same reason; use `=' with all other
symbols, for consistency; add explicit .obj extension to some lists of
object files passed to the linker; general cleanup of the command text
echoed during execution.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@7708 138bc75d-0d04-0410-961f-82ee72b054a4