This should fix linking with OpenMPI 1.5 and OpenMPI 1.6 (Issue #21)
 - rewrites the symbols in libevent to prefix with gl_
 - Added redefines which allow the rewritten symbols to be used correctly.
Modified the README so we are no longer incompatible with OpenMPI 1.5 and 1.6
Merge pull request #23 from ylow/master

This should fix linking with OpenMPI 1.5 and OpenMPI 1.6 (Issue #21)