touch: inject touches from spiceapi to native touch hooks (#824)

## Link to GitHub Issue or related Pull Request, if one exists
Fixes #814

## Description of change
Touches via the API wasn't being delivered to native touch hook;
implement this, which closes the last gap we have vs. wintouchemu.

While we're here, implement popn subscreen support for companion as
well.

## Testing
Tested for iidx/sdvx/popn

src/spice2x/touch/native/nativetouchhook.h

@@ -2,5 +2,9 @@
 
 namespace nativetouch {
     void hook(HMODULE module);
+
+    // true once hook() has installed the native touch stack for the current game;
+    // such games consume touch through the GetTouchInputInfo hook rather than spicetouch
+    bool is_hooked();
 }