IMPORTANT:  4.2.0 C/C++ Linkage Issue

This fixes a fairly major linkage issue with libtorque.so.2 in 4.2.0 which prevents OpenMPI jobs from starting.

During the TORQUE build process, C files are being compiled into object files using the C++ compiler (typically `g++`).  However, because all the component files of the libraries and executables are `*.c` and `*.h` files, they are being linked with `gcc` instead of `g++`.  This prevents the appropriate libraries (`libstdc++` and `libg++`) from being linked into, for example, `libtorque.so.2`.

Unfortunately, if one has an existing OpenMPI installation which is compiled against libtorque (for `tm` module support), attempts to replace the 4.1.x `libtorque.so.2.0.0` with the 4.2.0 `libtorque.so.2.0.0` will cause all MPI jobs to fail with an error message similar to this one:

    mca: base: component_find: unable to open
    /global/software/sl-6.x86_64/modules/intel/2011.11.339/openmpi/1.6-intel/lib/openmpi/mca_plm_tm:
    /usr/lib64/libtorque.so.2: undefined symbol: __gxx_personality_v0

This is caused by the aforementioned libraries being missing from the dependency tree for the new `libtorque.so.2.0.0` from torque 4.2.0.

This pull request references a fix for this issue.  It forces the torque build process to use `g++` (or, more specifically, `$(CXX)`) for linking instead of `gcc` (`$(CC)`).  Our testing shows that this allows `libtorque.so.2.0.0` to be a drop-in replacement for the previous version (as it should be, given the lack of change to the SOVERSION).