. add a by-extension preprocessing mechanism. A default preprocessor can
  be defined.
. change preferences used to define preprocessors

Conflicts:
	configure.ac

. the same state was used for the src and the tgt of the transition
. the label of the transition was not unreferenced.

place of the one storing state variables.

the type of the compiled expression. This type is also used to get enum
values that are not declared in the global enumeration.

enumeration.

parameter used to locate the error in a file.
. replace ccl_error in INTERP_EXCEPTION_MSG

. handle ENUM type

- use ENUMERATION to encode global symbols

in assertions or transitions

Conflicts:
	configure.ac