move amd64-specific (but os-independent) pieces of runtime
into amd64/ directory.

split rt2_amd64.c into closure.c and traceback.c.

TBR=r
OCL=26678
CL=26678
4 files changed
tree: 80d7ab5845634b7f1a43a4f98857b77d5589e413
  1. doc/
  2. include/
  3. lib/
  4. pkg/
  5. src/
  6. test/
  7. usr/