Avoid using UINT16 and similar typedefs, which are non-standard in the
iPXE codebase and generate conflicts when trying to include any of the
EFI headers.

Also fix trailing whitespace in the affected files, to prevent
complaints from git.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.