Fix ObjectSpace.count_objects document.
Merge pull request #2013 from take-cheeze/objectspace

Fix ObjectSpace.count_objects document.
Fix 'make test' fail to build on Windows(MSVC)
Merge pull request #2014 from kyab/fix_msvc_build_test

Fix 'make test' fail to build on Windows(MSVC)
Add detection of VC++2010 in build_config.rb
Merge pull request #2015 from kyab/detect_vc2010_build_config

Add detection of VC++2010 in build_config.rb
Add args in Enumerator#inspect
add tests for FalseClass

reorder and add tests for 15.2.6.1
Pass gem's version information to compilers.
remove tests for unicode chars in regular expression literals.

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.
Always increment `total` field of `os_count_struct` in callback.
Check sum of `ObjectSpace.count_objects` values is twice of total objects count.
(Which is CRuby's behavior.)
Merge pull request #2020 from iij/pr-remove-unicode-escape-tests

remove tests for unicode chars in regular expression literals.
Merge pull request #2019 from monaka/pr-add-macro-for-mrbgem-version

Pass gem's version information to compilers.
Merge pull request #2018 from akuroda/pr_false_test

add tests for FalseClass
Merge pull request #2021 from take-cheeze/count_objects_total

Always increment `total` field of `os_count_struct` in callback.
Merge pull request #2017 from suzukaze/fix_enumerator.inspect

Add args in Enumerator#inspect
wrap args by parens
should have passed args to to_enum
Delete khash_mask macro.
And fix expression to more simple and readable.
Use kh_end instead to n_buckets