Use fromstring() instead of fromarray()

Trac#11912 PIL < 1.1.7 fromarray doesn't handle 16 bit images properly, use fromstring as a workaround
Merge pull request #63 from manics/rebased/dev_5_0/pil_16bit-11912

Use fromstring() instead of fromarray() #11912 (rebased onto dev_5_0)