- flag for an option to set if changing it will trigger a new 'make depend'
- same for 'make clean'
- Specify files to be removed on clean.
- static compilation
- generating tags files
- grep is used for the gcc 3.4 compilation patch. It's slower now,
  and presence for "grep" isn't even checked.


some docs
- uqm_LDFLAGS etc are only relevant in the top dir
- some variables are 'inherited' from parent dir
- files are sourced (.)