Conversion from Cairo image to Form smells to be unnecessarily slow

[tinchodias]

Profile:

| aSurface |
aSurface := AeCairoImageSurface
    extent: 16@16
    format: AeCairoSurfaceFormat argb32.
aSurface asFormARGB32

and get:

We should check if it's true that FFIExternalArray >> resolveType takes 36.9ms (71% of total time!?)

[tinchodias]

The number of milliseconds was exaggerated in the output, I think, but the following results evidence resolveType: is significant:

| aSurface |
aSurface := AeCairoImageSurface
    extent: 16@16
    format: AeCairoSurfaceFormat argb32.
[aSurface asFormARGB32] bench.  
"164,764 iterations in 5 seconds 3 milliseconds. 32933.040 per second --> current"
"213,155 iterations in 5 seconds 1 millisecond.  42622.476 per second --> resolveType result hardcoded"

For the moment I will workaround with the hardcoded subclass that performs resolveType: on load, in class initialize.

[tinchodias]

Profiler now shows:

I don't trust too much on this. But above's bench output makes me think 997fac0 does speedup a bit.