Darwin : Begin rework of zero-fill sections.

Darwin : Begin rework of zero-fill sections.

Much of the existing work in the Darwin BSS and common sections
was to accommodate the PowerPC section anchors.  We want to segregate
this, since it might become desirable to support section anchors for
arm64.

First revision (here) is to use the same section conventions as the Xcode
toochains for BSS and COMMON.

We also drop the constraint about putting small items into data/static data
that was a work-around for Java issues (irrelevant for several editions).

gcc/ChangeLog:

	* config/darwin.c (darwin_emit_local_bss): Amend section names to
	match system tools. (darwin_output_aligned_bss): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/darwin-sections.c: Adjust test for renamed BSS and common
	sections.  Cater for 64 and 128 bit long doubles.