Fixed lots of warnings.

Rev: src/cpp.c:1.7
Rev: src/lex.c:1.38
Rev: src/main.c:1.34
Rev: src/modules/Image/encodings/gif.c:1.26
Rev: src/modules/Regexp/pike_regexp.c:1.10
Rev: src/modules/spider/spider.c:1.50
Rev: src/pike_types.c:1.28
Rev: src/signal_handler.c:1.21