Missing ostream insertion opertator (operator<<) for __intcap

[gcjenkinson]

The V8 Javascript/WASM engine attempts to print a __intcap using the ostream insertion operator (operator<<). In CheriABI overload resolution fails for __intcap (uintptr_t/intptr_t) as this type is no longer the same width as size_t. Adding overloads to the standard C++ library obviates the need for disruptive workarounds across the code base.