tools/docker: Fix a few bugs, add ubuntu 18.04 dockerfiles

Fix some warnings

Update pocl webpage with 1.2 release

Nitpicking CHANGES.

lib/kernel: fix shuffle() / shuffle2() implementation

* removes 3-el shuffle(), as is not defined for vectors of size 3
* Addressing vector elements using array-style indexing is not legal
  in OpenCL; rewrite code to use unions of vectors and arrays.

Credit Andreas Beckmann for debian patches

Update pocl webpage with 1.1 release

Change wording ;)

Fix pocl#585 - note zlib-dev requirement in documentation

Fix pocl.pc