Fixed lots of warnings.

Rev: src/builtin_functions.c:1.235
Rev: src/cpp.c:1.59
Rev: src/dynamic_load.c:1.37
Rev: src/las.c:1.160
Rev: src/lexer.h:1.15
Rev: src/modules/Image/colors.c:1.30
Rev: src/modules/Image/default_font.c:1.2
Rev: src/modules/Image/encodings/avs.c:1.8
Rev: src/modules/Image/encodings/iff.c:1.4
Rev: src/modules/Image/encodings/ilbm.c:1.13
Rev: src/modules/Image/encodings/pcx.c:1.9
Rev: src/modules/Image/encodings/psd.c:1.14
Rev: src/modules/Image/encodings/ras.c:1.5
Rev: src/modules/Image/encodings/tga.c:1.9
Rev: src/modules/Image/encodings/wbf.c:1.4
Rev: src/modules/Image/encodings/xcf.c:1.12
Rev: src/modules/Image/image.c:1.158
Rev: src/modules/Image/layers.c:1.41
Rev: src/modules/_Charset/charsetmod.c:1.18
Rev: src/modules/_Crypto/rsa.c:1.10
Rev: src/modules/files/file.h:1.15
Rev: src/modules/files/file_functions.h:1.15
Rev: src/modules/files/socket.c:1.47
Rev: src/modules/spider/xml.c:1.16
Rev: src/operators.c:1.85
Rev: src/pike_memory.c:1.52
Rev: src/pike_types.c:1.121
Rev: src/preprocessor.h:1.17
Rev: src/stralloc.c:1.78
Rev: src/svalue.c:1.62