Commit 40726f16a8 broke references to sections within ADDR(), and
overlays with weird section names.
* ldgram.y (paren_script_name): New rule.
(exp): Use it for ALIGNOF, SIZEOF, ADDR, and LOADADDR. Similarly
ensure script mode parsing for section name in SEGMENT_START.
(overlay_section): Delete unnecessary ldlex_script call. Backup
on a lookahead NAME parsed in expression mode.
* testsuite/ld-elf/overlay.s: Add more sections.
* testsuite/ld-elf/overlay.t: Test '-' in section names.
