make test/assert.rb cruby compatible
add test/bintest.rb
add conf.enable_bintest and run_bintest
add regression for #1564
add regression for #1572
add regression for #1563
enable bintest for travis CI
add a comment for enable_bintest in build_config.rb
declare struct mrb_irep.
Merge pull request #1590 from iij/pr-declare-struct-mrb-irep

declare struct mrb_irep.
Make mrb->arena variable sized.  Use MRB_GC_FIXED_ARENA for old behavior.
You will not see "arena overflow" error anymore, but I encourage gem authors
to check your gems with MRB_GC_FIXED_ARENA to avoid memory broat.
build with MRB_GC_FIXED_ARENA.
Automatically detect toolchain if it is visualcpp, and hence we drop vs2010.rake altogether - it’s no longer needed.
Merge pull request #1591 from iij/pr-fixed-arena-on-travis

build with MRB_GC_FIXED_ARENA on travis
Merge pull request #1592 from perlun/auto-toolchain

Automatically detect toolchain if it is visualcpp, and hence we drop vs2010.rake altogether - it’s no longer needed.
Updated the documentation to better match the way things work now that 172cd28 is merged.
Modify build script for gcc.

Newly added compile option '-std=gnu99' is not necessary for C++.
And 'g++' should be used to compile for C++ source codes, I think.
Modify referenced environment variables.

'CXX' is used instead of 'CC'.
'CXXFLAGS' is used instead of 'CFLAGS'.
add enable_debug method to MRuby::Build and build debug version in travis-ci
fix realloc error