Talk about assertions in CodingStandards.md

with a string like "internal error"). Option (A) is to be preferred to

option (B).

Assertions In Tor

-----------------

Assertions should be used for bug-detection only.  Don't use assertions to

detect bad user inputs, network errors, resource exhaustion, or similar

issues.

Tor is always built with assertions enabled, so try to only use

`tor_assert()` for cases where you are absolutely sure that crashing is the

least bad option.  Many bugs have been caused by use of `tor_assert()` when

another kind of check would have been safer.

If you're writing an assertion to test for a bug that you _can_ recover from,

use `tor_assert_nonfatal()` in place of `tor_assert()`.  If you'd like to

write a conditional that incorporates a nonfatal assertion, use the `BUG()`

macro, as in:

	if (BUG(ptr == NULL))

		return -1;

Doxygen comment conventions

---------------------------