Update README.md - No need to used µSTL with fxSDK >= 2.9.0

README.md

@@ -1,6 +1,11 @@
 # µSTL 2.3 sources for Casio Graph 90+E
 
-Need to have a fully working gcc toolchain for SH3/SH4 architecture.
+
+With fxSDK 2.9.0 and above, the C++ standard library is already included within the toolchain, so it is not needed to install the µSTL library.
+
+So the following is only for fxSDK versions below 2.9.0.
+
+To install and use the µSTL library, you need to have a fully working gcc toolchain for SH3/SH4 architecture.
 
 Compilation is done by using the adhoc Makefile :
 `make` in the main directory