Added mutexes in the variable server listener thread and each variable server thread.
During checkpoint restart all of these mutexes are locked by the master thread to
stop accepting new connections and stop all read/writing to all variable server clients.
Communication is resumed after the checkpoint has been reloaded.
refs #168
Reorganized. Created a new top level include directory that will hold all of Trick's header files. Moved all of the Trick headers to this directory. Created a libexec directory that holds all of the executables that users don't need to execute directly. Changed all of the executables remaining in bin to start with "trick-". In the sim_services directories changed all source files to find the Trick headers in their new location. Since all of the include files are gone in sim_services, removed the src directories as well, moving all of the source files up a level. Moved the makefiles, docs, man, and other architecture independent files into a top level share directory. Renamed lib_${TRICK_HOST_CPU} to lib64 or lib depending on the platform we're currently on.
refs #63
