fix off-by-one error in attrsym

The allocation size for null-terminated character is lacking.
In actual, it is no problem in most case
because codegen_palloc allocates more a memory size than required size.
fix indent.
Add mruby-bin-mruby-config
mruby command should not execute program on "syntax only option(-c)".
chmod 755
Don't echo empty string. (Remove workaround for windows)
Merge pull request #1799 from cubicdaiya/issues/off_by_one_error2

fix off-by-one error in attrsym
Merge pull request #1800 from tmash06/fix_indent

fix indent.
Merge pull request #1802 from tmash06/fix_syntax_check_no_exec

mruby command should not execute program on "syntax only option(-c)".
Merge pull request #1801 from mattn/mruby-config

Add mruby-bin-mruby-config