Mogan v1.1.0 beta5: very fast

I tried very hard to improve the performance of Mogan ---- my distribution of GNU TeXmacs.

This version is very fast, because I compute the font_cache.scm in advance. Font finding is not well implemented in GNU TeXmacs, it takes a long time to find a font. I improved it.

I will organize the code and contribute back to GNU TeXmacs later after I release Mogan v1.1.0.