objdump -D of bss sections and -s with -j

objdump -D of bss sections and -s with -j

There is some inconsistency between the behaviour of objdump -D and
objdump -s, both supposedly operating on all sections by default.
objdump -s ignores bss sections, while objdump -D dissassembles the
zeros.  Fix this by making objdump -D ignore bss sections too.

Furthermore, "objdump -s -j .bss" doesn't dump .bss as it should,
since the user is specifically asking to look at all those zeros.

This change does find some tests that used objdump -D with expected
output in bss-style sections.  I've updated all the msp430 tests that
just wanted to find a non-empty section to look at section headers
instead, making the tests slightly more stringent.  The ppc xcoff and
spu tests are fixed by adding -j options to objdump, which makes the
tests somewhat more lenient.

binutils/
	* objdump.c (disassemble_section): Ignore sections without
	contents, unless overridden by -j.
	(dump_section): Allow -j to override the default of not
	displaying sections without contents.
	* doc/binutils.texi (objdump options): Update -D, -s and -j
	description.
gas/
	* testsuite/gas/ppc/xcoff-tls-32.d: Select wanted objdump
	sections with -j.
	* testsuite/gas/ppc/xcoff-tls-64.d: Likewise.
ld/
	* testsuite/ld-msp430-elf/main-bss-lower.d,
	* testsuite/ld-msp430-elf/main-bss-upper.d,
	* testsuite/ld-msp430-elf/main-const-lower.d,
	* testsuite/ld-msp430-elf/main-const-upper.d,
	* testsuite/ld-msp430-elf/main-text-lower.d,
	* testsuite/ld-msp430-elf/main-text-upper.d,
	* testsuite/ld-msp430-elf/main-var-lower.d,
	* testsuite/ld-msp430-elf/main-var-upper.d: Expect -wh output.
	* testsuite/ld-msp430-elf/msp430-elf.exp: Use objdump -wh
	rather than objdump -D or objdump -d with tests checking for
	non-empty given sections.
	* testsuite/ld-spu/ear.d,
	* testsuite/ld-spu/icache1.d,
	* testsuite/ld-spu/ovl.d,
	* testsuite/ld-spu/ovl2.d: Select wanted objdump sections.