Log Message:
lang/clang: Improve DragonFly support

1) Don't pass both gcc 4.4 and gcc 4.7 paths to the driver.  Detect
   if gcc47 is available and use those paths, otherwise fall back to
   gcc44.
2) Add support for exception handling
3) Add rdynamic support
4) Add gnu-hash style support
5) Fix (!!) crtstuff (This was obsolete, include PIE support)
6) Remove rpath-link
7) Remove unneeded duplicate libgcc handling
8) Make libgcc handling match gcc specs (different for gcc 4.4 and 4.7)
9) Update dragonfly driver test