Pad sections according to current script FILL.

When aligning input sections, we are supposed to take the fill pattern
from a FILL statement, if there is one in the output section statement.

ld/
	* ldlang.c (lang_size_sections_1 <lang_input_section_enum>): Use
	current "fill", not "output_section_statement->fill".
ld/testsuite/
	* ld-scripts/fill.d, * ld-scripts/fill.t, * ld-scripts/fill_0.s,
	* ld-scripts/fill_1.s, * ld-scripts/fill_2.s: New test.
	* ld-scripts/data.exp: Run it.