Fix yhirose#158

Fix yhirose#156 (yhirose#157)

Fixed `char` -> `int` conversion problem

Fixed error report problems

Code cleanup

Merge pull request yhirose#139 from yhirose/cut

Cut operator support

Fixed peglit problem and update README

Added more unit tests

Better error report

Merge pull request yhirose#124 from yhirose/cpp17

C++17 support