doc: Remove the @gol macro/alias

The @gol macro appears to have existed as a workaround for a bug in old
versions of makeinfo and/or texinfo.tex, where they would, in some types
of output, fail to emit line breaks in @gccoptlists.  After updating
texinfo.tex, I noticed that this behavior appears to no longer be
exhibited, instead, both acted correctly and inserted newlines.  The
(groff) manual output also appears unaffected.

gcc/ChangeLog:

	* doc/implement-c.texi: Remove usage of @gol.
	* doc/invoke.texi: Ditto.
	* doc/sourcebuild.texi: Ditto.
	* doc/include/gcc-common.texi: Remove @gol.  In new Makeinfo and
	texinfo.tex versions, the bug it was working around appears to
	be gone.

gcc/fortran/ChangeLog:

	* invoke.texi: Remove usages of @gol.
	* intrinsic.texi: Ditto.