Fix indentation issues.
Refactor tagging into an options parameter in radlib.

When I implemented tagging, I should really have taken a step back and figured
out the best way to do it rather than just hacking it in. There wasn't really a
need to implement parallel radlib functions for this: it kind of works if tags
are the only attribute option, but with salting coming in as well, it just
didn't make sense.

On the bright side, this actually results in a net loss of code with the test
suite still passing just fine. That's the sign of a good commit. I hope.
Move salting back into radlib.

My main motivation for putting it in radius.c was to avoid TSRMLS_FETCH(),
which is kind of ugly and slow, but realistically it belongs here. I was also
concerned about the dependency on PHP code, but the MPPE demangling code
already depended on PHP's internal MD5 implementation, so we're no worse off
there.
Fix a memory leak when salting values.