Fix C++ files detection for automatic C++ ABI enabling.

Hash#replace should copy default from original even when the default value of the original is not set

Use kh_end instead to n_buckets

Delete khash_mask macro

And fix expression to more simple and readable.

Add args in Enumerator#inspect

Always increment `total` field of `os_count_struct` in callback.

add tests for FalseClass

Pass gem's version information to compilers.

remove tests for unicode chars in regular expression literals.

Check sum of `ObjectSpace.count_objects` values is twice of total objects count.
(Which is CRuby's behavior.)

mruby does not parse escape characters in a regular expression
literal (ref #2007).  It is parsed by the external mrbgem that
provides Regexp class, if any.  These tests should not be in
mruby core but in the mrbgem.

reorder and add tests for 15.2.6.1

Add detection of VC++2010 in build_config.rb

Fix 'make test' fail to build on Windows(MSVC)

Fix ObjectSpace.count_objects document.

Update mruby-head installed on Travis CI

This way other projects can test against it.

Refactor MRuby::Gem::List#check.

* Create mrbgem table before dependencies check.
* Topoligical sort gem list.
* Check circular mrbgem dependency.