It turns out, `unix_time` is also monotonic, and is used as such, so I've
renamed the new functions to `mono_time_*`.
2018-07-08:
```
00:01 <@irungentoo> the idea used to be that the unix_time() function
could go backward in time but I think I might have started using it like
if it could not after I changed it so that it would never go back in time
```
This requires that every symbol, even if static (file-scope), is unique.
The idea is that we can easily run "whole" program static analysis on
programs that include monolith.h ("whole" is in quotes, as we don't
include dependencies like libsodium in this static analysis).
