Make getChar() return int

All the calls to this function are:
  yyCh = getChar();

and yyCh is an int. This solves a sign-change warning found by ICC:
cpp.cpp(427): warning #68: integer conversion resulted in a change of sign

Change-Id: I1fe00005ab5095316b49fb0a0b71bbb60141a57e
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>