Added some casts.

Rev: src/modules/Image/colortable.c:1.17
Rev: src/modules/Image/encodings/gif.c:1.7
Rev: src/modules/Image/encodings/pnm.c:1.2
Rev: src/modules/Image/lzw.c:1.6
Rev: src/modules/Msql/msqlmod.c:1.3
Rev: src/modules/Odbc/odbc.c:1.5
Rev: src/modules/Odbc/odbc_result.c:1.6