Implement syntax checking for C/C++ using Clang
Merge branch 'master' into clang

* master: (26 commits)
  Remove old provisioning script again
  Inhibit checkdoc on Cask files
  Simplify variable safety declarations
  Enable Cppcheck inline suppressions
  Add option to choose Cppcheck checks
  Fix accidental modification of option vars
  Add option filter for comma separated lists
  Use verbose error message in Cppcheck
  Parse XML output of Cppcheck
  Suppress superfluous output in Cppcheck
  Install cppcheck in test environment
  Improve wording and formatting in credits
  Update introduction and changelog
  Remove stray character
  Cleanup links in README
  Fix Elixir warning patterns [#108]
  Update to Elixir 0.10 for tests
  Split the base states
  Move all states/pillars to base environment
  Improve pillar access for archive installations
  ...
Update introduction, changelog and credits
Demote Clang warning level to -Wextra

-Weverything is not intended for use on code, see
http://programmers.stackexchange.com/a/124574 for information.
Make option-list take a function to prepend
Improve docstrings
Make enabled Clang warnings customizable
Make test resources match test name
Make Clang include path customizable
Disable Clang for Cppcheck tests
Chain Cppcheck after Clang
[Fix #172] Merge branch 'clang'

* clang:
  Chain Cppcheck after Clang
  Disable Clang for Cppcheck tests
  Make Clang include path customizable
  Make test resources match test name
  Make enabled Clang warnings customizable
  Improve docstrings
  Make option-list take a function to prepend
  Demote Clang warning level to -Wextra
  Update introduction, changelog and credits
  Implement syntax checking for C/C++ using Clang
Fix clang tests

Disable Cppcheck during these tests
Add missing defcustom keywords
Give custom args for config file variables
Do not implicitly mark config file vars as safe
Explicitly declare variable safety of custom vars