format: add a custom formatter for std::type_info

format: add a custom formatter for std::type_info

The name() returned by std::type_info is implementation-dependant. In
practice, it is typically the type's mangled name. For GCC and clang, it
is possible to use abi::__cxa_demangle to demangle the name at runtime
while formatting a string.

If this poses any compatibility problem on other platforms, we can
fallback to using name() directly.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ib80babe4039c91ce6fdf6d9a9442c31645a43b08