* Move compiler/ under vlib/compiler/ .
* Add a minimal compiler/main.v driver program.
* Cleanup compiler/main.v .
* Make most compiler tests pass again.
* Apply the fix by @joe-conigliaro , so that the rest of the compiler tests are fixed too.
* Thanks to @avitkauskas, now the vlib/vcompiler/tests/str_gen_test.v test does not need to be special cased anymore.
* Reapply @joe-conigliaro fix for vgen.
