fix build issues with combinations of NUCSYN, MINT and DEBUG

renamed pthread mutexes to an array, with definitions in binary_c_mutexes.def
This makes it easier to init and destroy the mutexes when the store is built and freed.

new "binary_c_install" option which, currently, is the same as "binary_c_install_legacy" but is less typing.

updated docs to include the above change and -Dvalgrind=true