bugfixes:
  - get_url module - Removed out-of-date documentation stating that ``hashlib`` is a third-party library.
  - get_url module - Added a documentation reference to ``hashlib`` regarding algorithms,
                     as well as a note about ``md5`` support on systems running in FIPS compliant mode.
  - module_utils/basic.py - Fix detection of available hashing algorithms on Python 3.x.
                            All supported algorithms are now available instead of being limited to a hard-coded list.
                            This affects modules such as ``get_url`` which accept an arbitrary checksum algorithm.
