add macro ARY_SHARED_P
add macro ARY_SET_SHARED
add macro ARY_UNSET_SHARED
Please add me to the author.
use C style comments instead of C++ style comments

According to CONTRIBUTING.md,

Don't use C++ style comments

 /* This is the prefered comment style */

Use C++ style comments only for temporary comment e.g. commenting out some code lines.
remove unnecessary .gitkeep
add _FLAG to SET_SHARED macros; ref #1750
need to initialize flags for pooled strings; close #1768
revert changes to mrbconf.h
exception in fiber should make resume to raise in parent fiber context; close #1765
should build "all" before "test"; close #1774
support c++ exception
fix compile error
add cxx_abi travis test
fix compile error of min/max macro
move jmpbuf_id to generated file
name c++ abi build
use g++ to link
revert wrong build_config.rb
wrap scope with do {} while()