VC5Decompressor: place 'exceptionThrown' atomic in it's own cache line
VC5Decompressor: place 'exceptionThrown' atomic in it's own cache line

This measures as performance-neutral, but i'm pretty sure it's the rigth thing to do.

darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed