“Section 205 of the Evidence Act excludes the calling of evidence to contradict the answers given by a witness to questions which are relevant only so far as they tend to shake his credit by injuring his character, but Sections 207, 208 and 209 (c) clearly and expressly permit the calling of evidence to impeach a witness’ credit by proof of former statements inconsistent with any part of his evidence which is liable to be contradicted, as long as the witness has been cross-examined about the statements. Section 198 is to the like effect.”