add symbol lookup functions for dfsdl and dfimg

Author: dhthwy

library/include/modules/DFSDL.h

@@ -39,6 +39,8 @@ bool init(DFHack::color_ostream &out);
  */
 void cleanup();
 
+DFHACK_EXPORT void * lookup_DFSDL_Symbol(const char *name);
+DFHACK_EXPORT void * lookup_DFIMG_Symbol(const char *name);
 DFHACK_EXPORT SDL_Surface * DFIMG_Load(const char *file);
 DFHACK_EXPORT SDL_Surface * DFSDL_CreateRGBSurface(uint32_t flags, int width, int height, int depth, uint32_t Rmask, uint32_t Gmask, uint32_t Bmask, uint32_t Amask);
 DFHACK_EXPORT SDL_Surface * DFSDL_CreateRGBSurfaceFrom(void *pixels, int width, int height, int depth, int pitch, uint32_t Rmask, uint32_t Gmask, uint32_t Bmask, uint32_t Amask);

library/modules/DFSDL.cpp

@@ -107,6 +107,18 @@ void DFSDL::cleanup() {
     }
 }
 
+void * DFSDL::lookup_DFSDL_Symbol(const char *name) {
+    if (!g_sdl_handle)
+        return nullptr;
+    return LookupPlugin(g_sdl_handle, name);
+}
+
+void * DFSDL::lookup_DFIMG_Symbol(const char *name) {
+    if (!g_sdl_image_handle)
+        return nullptr;
+    return LookupPlugin(g_sdl_image_handle, name);
+}
+
 SDL_Surface * DFSDL::DFIMG_Load(const char *file) {
     return g_IMG_Load(file);
 }