Merge branch 'master' of github.com:mruby/mruby
introduce mrb_exc_new_str_lit for C string literals
Use mrb_exc_new_str_lit widely
Merge pull request #1789 from cubicdaiya/feature/mrb_exc_new_str_lit

Introduce mrb_exc_new_str_lit for C string literals
Fix Float#divmod.
add tests for Integer#divmod.
Merge pull request #1790 from iij/pr-float-divmod

fix Float#divmod returns nil
add Integer#div and Float#div.
Merge pull request #1791 from iij/pr-numeric-div

add Integer#div and Float#div to mruby-numeric-ext
fix a comment end of include guard
fix off-by-one error in String#rindex(fixnum)

null-terminated string should not be included in search targets.
Merge pull request #1792 from cubicdaiya/issues/fix_invalid_comment

fix a comment end of include guard
Merge pull request #1795 from cubicdaiya/issues/off_by_one_error

fix off-by-one error in String#rindex(fixnum)
Fix #1793
update compilation notes
fix typo
Merge pull request #1796 from mattn/fix_1793

Fix #1793
Merge pull request #1797 from take-cheeze/doc_update

Add notes about new features.
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.