Remove API's loot_cleanup() function

It's no longer required as the message string is not manually allocated,
its lifetime is tied to that of the library.

include/loot/api.h

@@ -309,11 +309,6 @@ extern "C"
      */
     LOOT_API unsigned int loot_get_error_message(const char ** const message);
 
-    /**
-     *  @brief Frees the memory allocated to the last error details string.
-     */
-    LOOT_API void loot_cleanup();
-
     /**@}*/
     /**********************************************************************//**
      *  @name Version Functions

src/api/api.cpp

@@ -269,11 +269,6 @@ LOOT_API unsigned int loot_get_error_message(const char ** const message) {
     return loot_ok;
 }
 
-// Frees memory allocated to error string.
-LOOT_API void     loot_cleanup() {
-    extMessageStr.clear();
-}
-
 //////////////////////////////
 // Version Functions
 //////////////////////////////

src/tests/api/test_api.h

@@ -76,31 +76,6 @@ TEST(GetErrorMessage, HandlesInputCorrectly) {
     ASSERT_STREQ("Null message pointer passed.", error);
 }
 
-TEST(Cleanup, CleansUpAfterError) {
-    // First generate an error.
-    EXPECT_EQ(loot_error_invalid_args, loot_get_error_message(NULL));
-
-    // Check that the error message is non-null.
-    const char * error;
-    EXPECT_EQ(loot_ok, loot_get_error_message(&error));
-    ASSERT_STREQ("Null message pointer passed.", error);
-
-    ASSERT_NO_THROW(loot_cleanup());
-
-    // Now check that the error message pointer is null.
-    error = nullptr;
-    EXPECT_EQ(loot_ok, loot_get_error_message(&error));
-    EXPECT_EQ(nullptr, error);
-}
-
-TEST(Cleanup, HandlesNoError) {
-    ASSERT_NO_THROW(loot_cleanup());
-
-    const char * error = nullptr;
-    EXPECT_EQ(loot_ok, loot_get_error_message(&error));
-    EXPECT_EQ(nullptr, error);
-}
-
 TEST_F(OblivionTest, CreateDbHandlesValidInputs) {
     EXPECT_EQ(loot_ok, loot_create_db(&db, loot_game_tes4, dataPath.parent_path().string().c_str(), localPath.string().c_str()));
     ASSERT_NO_THROW(loot_destroy_db(db));