random: remove compat.h include

We no-longer need ssize_t.

Add windows.h, which was being indirectly included via compat.h. It isn't
actually included in compat.h itself, but was being included as a side-effect
of other includes, like winsock2.h.

src/random.cpp

@@ -10,7 +10,7 @@
 #include <crypto/sha512.h>
 #include <support/cleanse.h>
 #ifdef WIN32
-#include <compat/compat.h>
+#include <windows.h>
 #include <wincrypt.h>
 #endif
 #include <logging.h>