symbols, asserts, profiling, and optimization.
Also much refactoring, improved help, and --enable-<foo> options will
now emit errors on nonsense (e.g.: --enable-foo="asdfasdf").
The libhdf5.settings.in file was also reformatted.
Tested on: 64-bit Ubuntu 15.10 (Linux 4.2.0 x86_64) gcc 5.2.1
serial and parallel autotools w/ various options