scons: Add warning for missing declarations

This patch enables warnings for missing declarations. To avoid issues
with SWIG-generated code, the warning is only applied to non-SWIG
code.

X86: Sometimes CPUID depends on ecx, so pass that in.

includes: use base/types.hh not inttypes.h or stdint.h

X86: Implement CPUID with a magical function instead of microcode.