libstd/{arm, x86}: Add helpers for 64 bit division

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>
libstd: vsnprintf: Add support for long long

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>
kernel: Add basic testing framework

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>