Log: new debugging category: Cps_transformation
OMakefile: building support/libextension is not necessary.
Cpsvar: suppress warnings.
Doc: add support for L keywords
New module : Cpstransform_rules, that compiles pattern matching.
Doc: add a figure to explain pattern compilation.
Extlist,Extmap: change the order of arguments for foldk:

The continuation should be the last argument, as is the case for all
other CPS-style functions
Cpstransform: update comments + some code cleanups