* module/language/elisp/parser.scm: New parser file.
* module/language/elisp/lexer.scm: Fix lexer/1 and add unquote-splicing support.
* module/language/elisp/spec.scm: Use new elisp-reader.
* module/language/elisp/README: Document we've got a reader now.
* test-suite/tests/elisp-reader.test: Test the parser.
