pdCanvas: failsafe for UI DIBs that fail to load in the IDE

No idea why the IDE will randomly fail to create the icon coordinate DIB
in the canvas status bar, but it's easy enough to work around...
Color management: various performance improvements

First, thanks to LaVolpe for the suggestion that images with embedded
sRGB profiles can entirely skip the color management step.  This not
only improves load performance, but also minimizes quantization errors
if the user has opted for fast-over-accurate color handling.

Also in this commit, when caching the system color profile, PD will now
check to see if the current system color profile is sRGB-compatible.
For the vast majority of casual users, this will be the case, and we can
use this knowledge to bypass certain color management steps, further
improving performance.
Viewport (and elsewhere): optimize color management for sRGB-compatible DCs

See previous commit for details; basically, PD will now dynamically
deactivate color management for DCs using sRGB color profiles.  For most
casual users, this should provide a performance boost.