remove MRUBY_VERSION for the time being; close #700
Remove redundant null checks.
Extract each expresion in "if" statements. It is for maintainability.
Merge pull request #709 from monaka/pr-remove-redundant-null-checks

Remove redundant null checks.
Merge branch 'master' of github.com:mruby/mruby into pr-strict-error-checking
Fix error handlings.
Add a comment: the usage of MRB_DUMP_GENERAL_FAILURE.
Merge pull request #710 from monaka/pr-strict-error-checking

Strict runtime error checking
Added s flag to ar command
Added conf.bins for defining bulding binaries
jump address error when value taken from if statement without else clause; close #712
Merge pull request #713 from masuidrive/add_s_options_to_ar

Added s flag to ar command
Merge pull request #714 from masuidrive/add_flags_for_building

Added conf.bins for defining bulding binaries
Make conf.bins work for cross compiled deps as well as the host.
Test ruby library should depend on host's mrbc, not its own mrbc
Merge pull request #717 from xxuejie/master

Host's mrbc file should be used when cross-compiling mrbtest.c
Merge pull request #716 from carsonmcdonald/crossdepfix

Make conf.bins work for cross compiled deps as well as the host.