Cleanup some standard #include file names

Cleanup some standard #include file names

* Use C++ standard include names rather than old C names (but only in
`*.cpp` files, and `*.h` where appropriate).  For example, use <cstdio>
or <cstdint> rather than <stdio.h> or <stdint.h>

* Make sure to use C-style include names in `*.c` files.  For example
<assert.h> rather than <cassert>

* Remove many (but not all) <shlwapi.h>

* Remove <cstdint>, <cstdarg>, <stdint.h> where not actually necessary