fix some incorrect pointer types as required by newer gcc compilers

[lijun99]

I fixed some code which are reported as "incorrect pointer/type" error by newer versions of gcc. The updated code can be compiled by Apple Clang as well.

@CunrenLiang, please make sure the changes don't break the code.

[lijun99]

Sorry, my editor prefers to remove all the empty spaces in the end. The actual changes are not that many,

1. snaphu.h, snaphu_utils.c, change the IsFinite function to int type, and use isfinite function from math.h;
2. contrib/alos2filter/src/psfilt1.c change the
   p_forward = fftwf_plan_dft_2d(fftw, fftw, (fftw_complex *)seg_fft[0], (fftw_complex *)seg_fft[0], FFTW_FORWARD, FFTW_MEASURE);
   p_backward = fftwf_plan_dft_2d(fftw, fftw, (fftw_complex *)seg_fft[0], (fftw_complex *)seg_fft[0], FFTW_BACKWARD, FFTW_MEASURE);
   to
   p_forward = fftwf_plan_dft_2d(fftw, fftw, (fftwf_complex *)seg_fft[0], (fftwf_complex *)seg_fft[0], FFTW_FORWARD, FFTW_MEASURE);
   p_backward = fftwf_plan_dft_2d(fftw, fftw, (fftwf_complex *)seg_fft[0], (fftwf_complex *)seg_fft[0], FFTW_BACKWARD, FFTW_MEASURE);
   since fftw_complex is of double type.
   also changed the IsFinite function;
3. graphx_mdx.c, enforce a type conversion for XmProcessTraversal: it returns a bool, but the XtCallbackProc should be a void type.

[bjmarfito]

Tested on Linux and macOS with GCC 14 and it works. Thank you @lijun99!

Can this be tested and merged @rtburns-jpl since we have a new system and we can only use GCC 14 and newer? Thanks!