Add a test for defun font-locking; add make check target to run it
Revert "Rename lua--function-name-rx, use it in font-lock keywords init"

This reverts commit 1d8dc5572be40071b61c5027a9c7fdcb68495e5c.
Move font-lock test helpers into a separate file
Font-lock "nil", "true" and "false" as constants rather than keywords
Make builtin font-locking more stable; enable it after ".." operator

Instability was caused by an attempt to handle multiline 'funcname'
nonterminals which is useless unless font-lock region is expanded
properly.