Jessie-> Stretch lib changes

[Brian Beuken]

After the book was written Raspbian Stretch was released (about 2 months after I submitted it, grrr), which is a nice update to the OS, but does mean that libs have changed,

I will adapt all code to work with Stretch, if you are using old Jessie, its time to update as Jessie is now considered to be over.

sudo apt-get update
sudo apt-get upgrade
This won't give you a version of Stretch more of a bit of both worlds, (you need to burn an new SD) but it will give you all new bits you need

you can also do
sudo apt-get dist-upgrade

Which will give you a full upgrade for your current version of Jessie  but with the new static libs, and retain all your current files avoiding the need for a full reburn of the SD but with the risk of some legacy libs still in place which may not work as expected now. (though if we're honest a full reburn is the best option here)

The only major complication is that there are now some new libs to use.

1. GLESv2_static 
   
2. EGL_static 
   
3. vchiq_arm 
   
4. vcos
   
5. khrn_static 
   
6. pthread 
   

in place of the 2 older GLESv2 and EGL libs
pthread is actually used a lot in the book, though the 1st few projects didn't need it, but with the expanded set of libs, pthread is now required also