Add display of CPU Temperature
Add CPU MHz
Merge pull request #71 from cigamit/System-Info

Add CPU Temperature and Frequency (fixed by  cigamit)
Update CMakeLists.txt

link whas changed for libpng 1.6.3 due to update and so md5 checksum failed, changed link so it should download and extracting again.
Update CMakeLists.txt
Update CMakeLists.txt