Remove unnecessary -lrt from CREST Makefile.
Remove unnecessary -lrt from CREST Makefile.

(This library is not available under Mac OS X, and is no longer needed
under Linux after revision r119.)

jburnim/crest,jburnim/crest,wy7980/crest,jburnim/crest,wy7980/crest,jburnim/crest,wy7980/crest,wy7980/crest