Adds an H5free_memory() function to the library for use with
functions that return library-allocated memory. The test and tool
code were modified to use this new function where it's appropriate.

Fixes HDFFV-7710, HDFFV-8519, and HDFFV-8551

Tested on:
    64-bit Windows 7 w/ VS2012
    32-bit LE linux w/ parallel and fortran (jam)
    32-bit LE linux w/ fortran and C++ (jam)


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@24937 dab4d1a6-ed17-0410-a064-d1ae371a2980