Have includes occur in the correct order

[cpha-trifork]

Changes

Includes are currently handled incorrectly. Whether they occur first or last in the file they are given precedence, as if they occurred last. So if you do

include "other.conf"

foo {
  a: 1
  c: 4
}

where other.conf is

foo {
  a: 2
  b: 3
}

the result is

foo {
  a: 2
  b: 3
  c: 4
}

with the value of a coming from the included file whereas, because the include occurs first in the file, the correct result should be a: 1.

This change fixes the problem though admittedly I don't understand the code well enough to know if it's the most appropriate solution. I also haven't added a test case since I could find no existing include tests. If you're interested in merging this I'm happy to add a test.