Revisit ICC correction on float data

[manthey]

We have a sample file (the one with sha512 ae05dbe6f3330c912893b203b55db27b0fdf3222a0e7f626d372c09668334494d07dc1d35533670cfac51b588d2292eeee7431317741fdb4cbb281c28a289115) which was converted to float32 pixels and has an ICC color profile. When we apply the ICC color profile (via PIL's tools), we really need to scale the data first. In general, when using ICC color profiles on data that is not uint8 and uint16, we probably should verify the data range beforehand.