Various fixes for text mode commands in latex.lang
These commits fix various problems in the "common-commands" context. To sum up, these commits mostly:
- move math-only commands to math contexts;
- remove obsolete, non-existant or inadvisable commands;
- remove duplicate commands matched elsewhere.
Finally, as my previous merge request was accepted, there is also a similar fix of bug #350 (closed) in this context.
Note: there is a typo in commit 44d63ccc one should read "common commands".