Fix for #82 and #85 OS X issues

Bump language-c version to handle new attribute syntax in OS X headers.
Fix #70: add nocode keyword for enum definitions

Also allow single quoted identifiers for enum aliases to help with
associated type enums.
Test case for #103
Possible fix for #103
Test case for #97
Test case for #65
AST and parser for const hooks
Fix for #65

Add const hook to access preprocessor constants.
Safe read for old and new .chi files
Tidy warnings
Version bump and clean-up for 0.19.1
Test case for #113
Fix #113
Possible fix for #111

Reorganise C2HS_MIN_VERSION macro to avoid defining it on the command
line passed to the pre-processor because this breaks NVIDIA's nvcc CUDA
compiler.
Try to get CUDA regression tests working again
Try to get CUDA install working *again*!
Travis and CUDA...
Trying to get CUDA build working...
CUDA install
Trying to get CUDA build working...