Merge branch 'topic/prebuild.sync.2015-05-20'

Merge branch 'topic/prebuild.sync.2015-05-20'

* topic/prebuild.sync.2015-05-20:
  Document tags [s-roff] and [s-roff-sync.1]
  Sync-to-go: doc (less info manual)
  Sync-to-go: man..
  Sync-to-go: tmac..
  Sync-to-go: src/ute-tfmtodit..
  Sync-to-go: src/ute-afmtodit..
  Sync-to-go: src/src-troff..
  Sync-to-go: src/src-roff..
  Sync-to-go: src/pre-tbl..
  Sync-to-go: src/pre-soelim..
  Sync-to-go: src/pre-preconv..
  Sync-to-go: src/pre-pic..
  Sync-to-go: src/pre-html..
  Sync-to-go: src/pre-grn..
  Sync-to-go: src/pre-eqn..
  Sync-to-go: src/dev-tty..
  Sync-to-go: src/dev-ps..
  Sync-to-go: src/dev-html..
  Sync-to-go: font/..
  Sync-to-go: contrib/pdfmark..
  Sync-to-go: contrib/hdtbl..
  s-gnu-diff.sh: easy compare codebase(s)
  Sync-to-go: update copyright for 2015