popn: boot with 3 monitors (#636)

## Link to GitHub Issue or related Pull Request, if one exists
#618 

## Description of change
Take the monitor hooks added for IIDX/SDVX #612 and apply it to popn as
well now that popn has a subscreen.

There is a debug option in game that actually uses three monitors, which
can be activated via hex edits. This will prevent that from working.

## Testing
Tested with 3 monitors, fs and windowed.

src/spice2x/util/sysutils.cpp

@@ -576,7 +576,13 @@ namespace sysutils {
     }
 
     void hook_EnumDisplayDevicesA() {
-        EnumDisplayDevicesA_orig = detour::iat_try(
-             "EnumDisplayDevicesA", EnumDisplayDevicesA_hook, avs::game::DLL_INSTANCE);
+        // the goal is to trick DX9 into thinking that some monitors are not attached
+        // so we need to trampoline hook at user32 instead of IAT at game level
+        log_misc("sysutils", "hooking EnumDisplayDevicesA to hide if there are more than 3 monitors...");
+        detour::trampoline_try(
+            "user32.dll",
+            "EnumDisplayDevicesA",
+            (void*)EnumDisplayDevicesA_hook,
+            (void**)&EnumDisplayDevicesA_orig);
     }
 }