C APIs to get and set capability properties

CHERI C/C++ supports a number of new APIs to get and set capability properties given a pointer argument. Although most software does not need to directly manage capability properties, there are some cases when application code needs to further constrain permissions or limit bounds associated with pointers. For example, high-performance applications may contain custom memory allocators and wish to narrow bounds and permissions on returned pointers to prevent overflows between its own allocations.