Memsqueeze fixes

Hi Marti.

I've been using Memento (my memory testing lib) to do some Memory Squeezing testing on Ghostscript. (We run gs repeatedly, arranging for it to fail after 1,2,3,4... memory allocations). This effectively forces us to test the allocation failure error cleanup code paths. I'm ignoring leaks for now, and concentrating on SEGVs.

I've found some in lcms, and I have patches for them (2 so far). I've put them on my github repo under the 'memsqueeze_fixes' branch. I've tried to follow lcms2 style as best I can, but I'll completely understand if you want to rework them before accepting them.

Thanks. Happy Easter!

Robin