wma: Doxify some comments. struct coef_vlc_table->levels and struct getbit_context had undoxified comments.
Add missing description of struct coef_vlc_table.
wmadata.h: Remove unused member max_level from struct coef_vlc_table.
Make all wma data tables static. They are only used in wmadec.c.
skip pointless ff_ prefix.
First draft of the wma decoder. Understands only v1, but is easy to crash.