It turns out we do need to backtrack when parsing after all. The
fill_opt component in the section rule swiches to EXPRESSION and back
to SCRIPT, and to find the end of an expression it is necessary to
look ahead one token.
* ldgram.y (section): Throw away lookahead NAME token.
(overlay_section): Likewise.
* testsuite/ld-elf/overlay.t: Add fill pattern on overlays.
Test fill pattern before stupidly named normal sections too,
and before /DISCARD/.