feat(d3dx): Implement D3DXMatrixIdentity and D3DXCreateFont (TheSuperHackers#2176)

Implement D3DXMatrixIdentity using WWMath and stub D3DXCreateFont for
disabled Generals Tools build.

1. D3DXMatrixIdentity - Full Implementation
   - Maps to Matrix4x4::Make_Identity() from WWMath
   - Used in 8+ locations, including water rendering (W3DWater.cpp)
   - Critical for clipping matrix initialization

2. D3DXCreateFont - Stub for Disabled Tools
   - Only used in disabled Generals Tools (apt, w3dviewer)
   - Build preset RTS_BUILD_GENERALS_TOOLS=OFF by default
   - Returns D3DERR_NOTAVAILABLE to indicate unavailable functionality
   - Acceptable stub for out-of-scope build targets

Alternative approaches evaluated:
- Matrix4x4::Make_Identity() found in WWMath (used for implementation)
- No existing game font system suitable for D3DXCreateFont
- GDI CreateFont possible but unnecessary for disabled build

D3DXMatrixIdentity completes matrix math coverage alongside existing
D3DXMatrixMultiply, D3DXMatrixRotationZ, D3DXMatrixTranspose.

Author: JohnsterID

Core/Libraries/Include/Lib/D3DXCompat.h

@@ -591,6 +591,24 @@ inline D3DXMATRIX* D3DXMatrixTranslation(D3DXMATRIX* pOut, float x, float y, flo
     return pOut;
 }
 
+/**
+ * D3DXMatrixIdentity - Initialize matrix to identity
+ * Maps to: Matrix4x4::Make_Identity()
+ * 
+ * Used in water rendering (W3DWater.cpp) for clipping matrix initialization.
+ * Implementation using WWMath (8+ uses across codebase).
+ */
+inline D3DXMATRIX* D3DXMatrixIdentity(D3DXMATRIX* pOut)
+{
+    if (!pOut) return pOut;
+    
+    Matrix4x4 identity;
+    identity.Make_Identity();
+    
+    *(Matrix4x4*)pOut = identity;
+    return pOut;
+}
+
 #endif // WWMATH_AVAILABLE
 
 //-----------------------------------------------------------------------------
@@ -934,6 +952,43 @@ inline HRESULT D3DXFilterTexture(
     return D3D_OK;
 }
 
+//-----------------------------------------------------------------------------
+// Font Functions (Stubs for unused functionality)
+//-----------------------------------------------------------------------------
+
+// Forward declaration for D3DX Font interface
+struct ID3DXFont;
+typedef struct ID3DXFont *LPD3DXFONT;
+
+/**
+ * D3DXCreateFont - Create D3DX font object
+ * 
+ * STUB: This function is only used in WorldBuilder tools (4 calls in wbview3d.cpp).
+ * WorldBuilder is NOT built in MinGW configuration (RTS_BUILD_GENERALS_TOOLS disabled).
+ * 
+ * Build scope: Tools only, not game executables (generalsv.exe, generalszh.exe)
+ * Usage locations:
+ *   - Generals/Code/Tools/WorldBuilder/src/wbview3d.cpp:543, 2205
+ *   - GeneralsMD/Code/Tools/WorldBuilder/src/wbview3d.cpp:560, 2286
+ * 
+ * If WorldBuilder support is needed in future:
+ * 1. Enable RTS_BUILD_GENERALS_TOOLS in CMake preset
+ * 2. Implement using GDI CreateFont + text rendering system
+ * 3. Or use existing game font system if available
+ * 
+ * Stub function acceptable when unused or out of build scope.
+ * This is consistent with D3DXCreateTextureFromFileExA approach (commit b9b1ea03).
+ */
+inline HRESULT D3DXCreateFont(
+    LPDIRECT3DDEVICE8 pDevice,
+    HFONT hFont,
+    LPD3DXFONT* ppFont)
+{
+    // WorldBuilder not in build scope - stub acceptable
+    if (ppFont) *ppFont = nullptr;
+    return D3DERR_NOTAVAILABLE;
+}
+
 #endif // __cplusplus
 
 #endif // NO_D3DX