Fixed a few warnings.

Rev: src/modules/CommonLog/clf.c:1.4
Rev: src/modules/HTTPLoop/accept_and_parse.c:1.18
Rev: src/modules/Image/encodings/gif.c:1.60
Rev: src/modules/Image/font.c:1.65
Rev: src/modules/Pipe/pipe.c:1.42
Rev: src/modules/files/file.c:1.189
Rev: src/modules/files/file.h:1.17
Rev: src/modules/files/sendfile.c:1.43
Rev: src/modules/system/nt.c:1.23
Rev: src/signal_handler.c:1.178