add .drrun native frontend support

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on November 27, 2013 13:31:32_

For embedding tools that have their own front-ends, like Dr. Memory and drstrace, into the DR package ( https://code.google.com/p/drmemory/issues/detail?id=1056 ), we'd like to have .drrun files that will launch the native frontend tool and pass options to it.

Do we need option mapping?

drmemory.drrun32:
add NATIVE_OPS=-dr ../../
DRRUN_OPS_MAP=-debug => -dr_debug
DR_OPS_PARAM=-dr_ops ""

We shouldn't if we just don't support things like:
bin32/drrun -debug -t drmemory <...>

And we force the user to say:
bin32/drrun -debug -t drmemory -dr_debub

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1329_