This primarily affects dependency headers and contrib code, as kresd now
uses kr_require() or kr_assume() instead of assert().

These macros should replace the use of assert() in our entire codebase.
assert() have the following issues:
  - can be turned off at compilation time
  - they don't have consistent meaning in our code

kr_require() behaves similarly to assert - it checks a condition and
aborts if it fails. Unlike asserts, these aren't turned off by using
-DNDEBUG. kr_require() should be used for non-recoverable errors.

kr_assume() is a way to check for non-fatal errors which supports error
reporing, debugging and recovery. The function returns a boolean value
which the caller must use for error handling. An error log message is
produced when the condition fails. Optionally, when kr_debug_assumption
is set to true, the process will use fork() and the child will abort().
This generates a coredump for debugging purposes, while allowing the
parent process to keep running and recover from the non-fatal error.
This can be useful for debugging hard to reproduce errors in production
environments.

daemon/http: expose HTTP headers to kr_request

Closes #616

See merge request !1165