C++: add an option to enable RTTI support

Closes https://github.com/espressif/esp-idf/issues/1684

Kconfig

@@ -245,9 +245,8 @@ mainmenu "Espressif IoT Development Framework Configuration"
                 memory for thrown exceptions when there is not enough memory on the heap.
 
         config COMPILER_CXX_RTTI
-            # Invisible option, until the toolchain with RTTI support is released.
-            # Use prompt "Enable C++ run-time type info (RTTI)" when updating.
-            bool
+            bool "Enable C++ run-time type info (RTTI)"
+            default n
             help
                 Enabling this option compiles all C++ files with RTTI support enabled.
                 This increases binary size (typically by tens of kB) but allows using