Add a mechanism for allowing code to check if it's in a unit test.

This is protected from general use/abuse through friendship. Generally
a bad idea to use this mechanism, and it has explicitly been made hard
to use through requiring friendship and a long class name to type that
makes you state you're aware that it's a bad idea before you can use
it.
Add a helper in <base> for accessing mlock.
Switch to <base/mlock.h>

NOTE: We don't do <orly/indy/fiber/fiber.h> because there not having
mlock'd memory will completely murder performance, and possibly cause
other badness.
Merge pull request #42 from cmaloney/dont_mlock_in_tests

Don't mlock in tests