add the C library headers MSVC needs

Unqualified uint8_t/size_t and friends were reaching 24 units through
some other header on libstdc++; MSVC's STL does not do that, which broke
gl/ubo.cppm (and made its UBS_PAD macro look like garbage). Also
silences C5244, MSVC's counterpart to the clang warning about glm being
included in the module purview, which is deliberate here.

scripting/PyInt.cpp

@@ -1,4 +1,6 @@
 module;
+#include <cstddef>
+#include <cstdint>
 #include <array>
 #include <chrono>
 #include <deque>