Move all id generation into transpile_context
Summary:
Having these in separate places and initialized at program launch
means that the generated units might differ nondeterminstically.
Instead, generate incrementing ids on a per-file basis by shoving the state in
Transpile_context.t
Also puts the location id generation behind a flag so we don't do it unless we actually want those IDs (which, we don't right now)
Reviewed By: JacksonGL
Differential Revision:
D15994933
fbshipit-source-id:
bd0d29889df491d4d21fc05d1e988187c9717486