Rename project in CMake

TODO: to create symlinks to the old names!
diff --git a/programs/util/CMakeLists.txt b/programs/util/CMakeLists.txt
index aedd94f..f302de7 100644
--- a/programs/util/CMakeLists.txt
+++ b/programs/util/CMakeLists.txt
@@ -1,5 +1,5 @@
 set(libs
-     polarssl
+     mbedtls
 )
 
 add_executable(strerror strerror.c)