[magick-developers] Moving math.h...

[Toyotomi]

With MSVS6 and ImageMagick 5.4.6, I must move math.h in studio.h
all the way to the top, before the conditional `extern "C"` stuff.
( I also needed to do this in previous version )

This is because Microsoft's math.h has one silly but also conditional
C++ template in it for pow. This is not supposed to be a problem, but
the following error is received :

  C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\math.h(514)
  error C2894: templates cannot be declared to have 'C' linkage

Moving math.h fixes the problem and I did at one time work out the
specific reason this happens, but am tired and forget now. I just
make the change every time I download a new version of ImageMagick.