[ptx] windows pairwise optimizer bug fixed

[Pablo d'Angelo]

Hi,

I finally found out what the cause for the crash of the pairwise
optimisation on Windows was:

On windows, one cannot assume that memory that is allocated with
malloc() can be freed again with free().

It only works if the dll and the application are build against the same
runtime library.

The panotools library build with Visual C was compiled against a different
runtime than the mingw produced executables, leading to a crash, since hugin
used some pano12.dll function to clean up data structures allocated within
hugin.

Now, I duplicated the release code inside hugin, and everything seems to
work fine.

I have also changed the optimisation code, now it uses the pano12
optimisation routine, that is the optimizer by Rik Littlefield.

ciao
  Pablo