fix false redeclaration error with CIgnore (2nd attempt)

previous fix only checked redeclarations not redefinitions and their suble different semantics
this version is more general now and ignores types with CIgnore entirely
Avoid type error wrong type argument to increment CObj(CIgnore())
 when incrementing a CIgnore, no type errors should be found

Conflicts:

	CTypeChecker/src/main/scala/de/fosd/typechef/typesystem/CExprTyping.scala
survive invalid .ast files

previously died with Assertion error
fix incorrect propagation of fexpr context

potentially reported errors in a too wide context
Merge branch 'master' of git://github.com/ckaestne/TypeChef