Fixed a few warnings.

Rev: src/gc.c:1.112
Rev: src/gc.h:1.60
Rev: src/interpret.c:1.161
Rev: src/interpret_functions.h:1.30
Rev: src/interpreter.h:1.50
Rev: src/modules/files/sendfile.c:1.41
Rev: src/modules/files/udp.c:1.14
Rev: src/modules/sprintf/sprintf.c:1.70