LD/testsuite: Add 2**4 section alignment FILL script statement test

LD/testsuite: Add 2**4 section alignment FILL script statement test

Complement commit ffe54b3798db ("Pad sections according to current
script FILL.") and add a FILL script statement test for targets that
impose the minimum alignment of more than 2**2 for the `.text' section.
These targets include IA-64 targets, MIPS targets other than bare-metal
ELF and VxWorks, TILE-Gx targets, TILEPro targets and X86-64 PE targets.

Use the `notarget' tag for configuration triplets that are incompatible
with the new test, but are supported by the existing FILL test, and
`xfail' for ones that have issues due to section alignment or padding
with both tests.  Make a complementary change to the existing FILL test,
removing the following test issues:

arm-epoc-pe  -FAIL: ld-scripts/fill
mips-elf  -XPASS: ld-scripts/fill
mips-img-elf  -XPASS: ld-scripts/fill
mips-mti-elf  -XPASS: ld-scripts/fill
mips-sde-elf  -XPASS: ld-scripts/fill
mips-vxworks  -XPASS: ld-scripts/fill
mipsel-elf  -XPASS: ld-scripts/fill
mipsel-img-elf  -XPASS: ld-scripts/fill
mipsel-mti-elf  -XPASS: ld-scripts/fill
mipsel-vxworks  -XPASS: ld-scripts/fill
mipsisa32-elf  -XPASS: ld-scripts/fill
mipsisa32el-elf  -XPASS: ld-scripts/fill
mipsisa64-elf  -XPASS: ld-scripts/fill
mipsisa64el-elf  -XPASS: ld-scripts/fill
tilegx-linux  -FAIL: ld-scripts/fill
tilepro-elf  -FAIL: ld-scripts/fill
tx39-elf  -XPASS: ld-scripts/fill

	ld/
	* testsuite/ld-scripts/fill.d: Adjust `xfail' entries.  Add
	`notarget' entries.  Update comments.
	* testsuite/ld-scripts/fill16.d: New test.
	* testsuite/ld-scripts/fill16_0.s: New test source.
	* testsuite/ld-scripts/fill16_1.s: New test source.
	* testsuite/ld-scripts/fill16_2.s: New test source.
	* testsuite/ld-scripts/data.exp: Run the new test.