png: K&R formatting cosmetics
png: Support rgb48 and rgba64 encoding
raw, nut: Support rgba64 encoding
img2: add j2c file extension

Some applications use the j2c extension for jpeg2000 codestream files.
tiff: Support rgba encoding
fraps: set color_range
mjpeg: set color_range
mdec: set color_range
ljpeg: check color_range
libx264: check color_range