dotnetframework-ms: Don't need to find recursive for csc.exe
makery: _TraceBegin() and _TraceEnd()
make: Trace MAKE_Shell() command lines
Add additional tracing

- MODULES_Use()
- Inclusion of individual files in MODULES_Use()
- Flattening of individual variables in PROJ_FlattenVars()
Optimise PROJ_Locate()

- Search in the Makery directory first
- Early-out when found
Tidy up tracing and debug printing
Cache-on-expand project variables when flattening

So they're only ever expanded once.  Significant speedup, especially on
Windows.