remove Class#alloc method
Merge branch 'master' of github.com:mruby/mruby
remove unnecessary return
Merge pull request #1479 from chenyukang/remove_return

remove a unnecessary return
android doesn't have log2
Merge pull request #1480 from wanabe/patch-1

android doesn't have log2
Merge branch 'master' of github.com:mruby/mruby
add x86_64-darwin host platform.
Merge pull request #1481 from suichu/patch

add x86_64-darwin host platform.
Merge branch 'master' of github.com:mruby/mruby
Added test case for String#start_with? with string of length 1.
Fix for string-length-related issue in String#start_with? logic.
Added test case for String#end_with? with string of length 2.
Fix for string-length-related issue in String#end_with? logic.
Refactor of String#end_with? comparison logic.
Refactor of String#start_with? comparison logic.
add mrb_string_type().
Check type of arguments for #start_with and #end_with.
Fix a problem of 'z' option and shared string
add Exception#backtrace