Simplify DLL hook mechanism

This change deletes the GetProcAddress hook and exports symbols
corresponding to the hooked functions from each hook DLL instead;
we stop at redirecting LoadLibrary/GetModuleHandle calls to the
hook DLL. This simplified approach has less hidden magic going on
behind the scenes and is more readily composable (i.e. a hook DLL
can export redirect symbols for more than one dynamically-loaded
DLL).

hooklib/dll.h

@@ -3,10 +3,6 @@
 #include <stddef.h>
 #include <stdint.h>
 
-#include "hook/table.h"
-
 HRESULT dll_hook_push(
         HMODULE redir_mod,
-        const wchar_t *name,
-        const struct hook_symbol *syms,
-        size_t nsyms);
+        const wchar_t *name);