synctex_parser.h and synctex_parser_utils.h are public headers that both
include synctex_version.h, but the latter isn't installed by the
autotools glue. Reported by ajacoutot@, ok kili@ edd@ (maintainer)
While here, the libsynctex API/ABI has changed between tl2017 and
tl2018, so bump the major (also bump the minor for libptexenc).
ok edd@ (maintainer)
f720122b3a