Fix mutually recursive definition lexp parsing

Changes to be committed:
* src/lparse.ml:
	- rollback to old lexp_decls implementation
	- renamed (lexp_decls) to (lexp_p_decls)
* tests/eval_test.ml: minor fixes
* src/eval.ml:
	- new functions (eval_call)/(eval_case)
	- modified eval_call to support partial application

renamed:    src/full_debug.ml -> src/debug_util.ml
* GNUmakefile: adapted to renamed files