[WIP] Merged the 2.064 frontend

This brings LDC to the level of D-Programming-Language/dmd@a913ce4bc59a94a022a27e390fc841f4aededffb, i.e. somewhere around the second 2.064 beta.

dmd-testsuite has not been updated yet, the script for handling the repository (ldc-developers/ldc-scripts/dmd-testsuite) would have to be modified to also extract all the branches (no beta has been tagged yet).

Currently failing test cases: https://gist.github.com/klickverbot/7075137

This also includes an implementation of the new ModuleInfo discovery/druntime startup scheme on Linux which supports shared libraries. It didn't cause any regressions, at least not other than in the test cases failing anyway. Actually using it with shared objects has not been tested yet, though.