First bugfix release in 2.7 series.

This has several critical fixes for possible segfault and deadlocks.

- Fixed critical issue with cyclic gc which resulted in segfaults
- Avoid unaligned access fixing h5py on sparc64
- Fixed compilation issues for some library locations
- Fix deadlock between phil and the import lock in py2
- Improve windows handling if filenames
- Allow close to be called on file multiple times
- Warn on loaded vs complied hdf5 version issues
- Fix overflow computing size of dataset on windows
- Do not mangle capitalization of filenames in error messages
- Fix longdouble on ppc64le
- Fix compounds structs with variable-size members