* Documentation/index.texi: Add pointers to new regression and

* Documentation/index.texi: Add pointers to new regression and
test documents.

* Documentation/user/converters.itely:
Documentation/user/invoking.itexi: Some small fixes for uniform
usage example.

* input/font20.ly, font-body.ly: New files, moved from input/test.

* input/test/different-time-signatures.ly: Add FIXME marker;
comment-out broken code.

* Documentation/regression-test.tely: Comment-out, add
obsolete-marker and url to regression-test-dir.

* input/test/GNUmakefile:
* input/regression/GNUmakefile: Add rule for lys-to-tely.py.

* input/regression/+.ly:
* input/test/+.ly: New file.