The `hash` command should be a builtin not an alias

[krader1961]

While working on the b_alias() function to make it the first builtin to use getopt_long() rather than optget() I noticed it has a gross hack to support the bash hash -r flag needed because hash is implemented as an alias of alias. Separate the hash logic from the alias logic so those hacks aren't needed.

[krader1961]

See also issue #238 where we are discussing removing the code that attempts, incorrectly and which can never be successful, to emulate bash.