Added cmake profiling support

Support for using gprof with gromacs executables is added to
allow basic profiling using
gmx command [options]
gprof gmx

Removed explicit -fomit-frame-pointer, since this has been default
behaviour in gcc at most optimization levels since at least version
4.4. This lets "-O3 -pg" in the Profile build-type CFLAGS fight it out
themselves.

Change-Id: I99710f9cdd406f866d663a9610e0e9cccb87c07c