Description:
    Bring in Chao/Neil/my changes to optimize hyperslab selection operations
further, along with 3 new public API routines: H5Scombine_hyperslab(),
H5Sselect_select() and H5Scombine_select(), along with many minor cleanups to
the code and fixing a few compiler warnings.

Tested on:
    Mac OSX/64 10.9.3 w/gcc 4.9.x and parallel w/OpenMPI
    (h5commttest forthcoming)


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@25273 dab4d1a6-ed17-0410-a064-d1ae371a2980