BUG: missing _foamEtc definition (fixes #38)

- this function definition (as per the OpenFOAM functions) is required
  for compatibility when sourcing some config files (eg, mpi).

etc/tools/ThirdPartyFunctions

@@ -143,6 +143,9 @@ fi
 # Source an etc/config.sh file
 _foamConfig() { eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh -config $@)"; }
 
+# Source an etc file (as per OpenFOAM functions). Eg, for mpi setup.
+_foamEtc() { eval "$($WM_PROJECT_DIR/bin/foamEtcFile -sh $@)"; }
+
 #------------------------------------------------------------------------------
 
 #