documentation fix: $ is in the main note...

Rev: src/modules/Image/blit.c:1.10
Rev: src/modules/Image/blit_layer_include.h:1.3
Rev: src/modules/Image/colortable.c:1.3
Rev: src/modules/Image/dct.c:1.8
Rev: src/modules/Image/doc/Image.font.html:1.3
Rev: src/modules/Image/doc/Image.html:1.4
Rev: src/modules/Image/doc/Image.image.html:1.7
Rev: src/modules/Image/font.c:1.13
Rev: src/modules/Image/image.c:1.31
Rev: src/modules/Image/image.h:1.8
Rev: src/modules/Image/lzw.c:1.2
Rev: src/modules/Image/lzw.h:1.3
Rev: src/modules/Image/matrix.c:1.6
Rev: src/modules/Image/operator.c:1.8
Rev: src/modules/Image/pattern.c:1.5
Rev: src/modules/Image/pnm.c:1.5
Rev: src/modules/Image/polyfill.c:1.4
Rev: src/modules/Image/quant.c:1.10
Rev: src/modules/Image/togif.c:1.15