[Add] Actually load the diff library in mission Lua.

src/misn_lua.c

@@ -168,6 +168,11 @@ static const luaL_reg diff_methods[] = {
   { 0, 0 }
 };
 
+static const luaL_reg diff_cond_methods[] = {
+  { "isApplied", diff_isappliedL },
+  { 0, 0 }
+};
+
 /* Register all the libaries. */
 int misn_loadLibs(lua_State* L) {
   lua_loadLephisto(L);
@@ -181,6 +186,7 @@ int misn_loadLibs(lua_State* L) {
   lua_loadHook(L);
   lua_loadPilot(L, 0);
   lua_loadMusic(L, 0);
+  lua_loadDiff(L, 0);
   return 0;
 }
 
@@ -189,6 +195,7 @@ int misn_loadCondLibs(lua_State* L) {
   lua_loadSpace(L, 1);
   lua_loadVar(L, 1);
   lua_loadPlayer(L, 1);
+  lua_loadDiff(L,1);
   return 0;
 }
 
@@ -219,6 +226,21 @@ int lua_loadHook(lua_State* L) {
   return 0;
 }
 
+/**
+ * @fn int lua_loadDiff(lua_State* L, int readonly)
+ *
+ * @brief Loads the diff Lua library.
+ *    @param L Lua State.
+ *    @param readonly Load read only functions.
+ */
+int lua_loadDiff(lua_State* L, int readonly) {
+  if(readonly == 0)
+    luaL_register(L, "diff", diff_methods);
+  else
+    luaL_register(L, "diff", diff_cond_methods);
+  return 0;
+}
+
 /* 
  * Run a mission function.
  * -1 on error, 1 on misn.finish() call and 0 normally.

src/misn_lua.h

@@ -15,4 +15,5 @@ int lua_loadMisn(lua_State* L);
 int lua_loadVar(lua_State* L, int readonly);
 int lua_loadPlayer(lua_State* L, int readonly);
 int lua_loadHook(lua_State* L);
+int lua_loadDiff(lua_State* L, int readonly);