Remove some roundoff from mrb_flo_to_str
Merge pull request #2532 from chasonr/float-to-string

Remove some roundoff from mrb_flo_to_str
Refactor flo_mod func in numeric.c
Fix indents in numeric.c
Merge pull request #2534 from suzukaze/refactor-numeric.c

Refactor flo_mod func in numeric.c
Merge pull request #2533 from suzukaze/fix-indents

Fix indents in numeric.c
removed unused variable in range_beg_len
Merge pull request #2535 from kkkkkt/remove-unused-variable

removed unused variable in range_beg_len
refactor class.c methods (fix indent, remove unneed temp value. )
use mrb_false_value instead of mrb_bool_value
Improve replacement math functions for Visual C++.
Merge pull request #2536 from kkkkkt/refactor-classc

Refactor classc
Merge pull request #2537 from chasonr/math-functions

Improve replacement math functions for Visual C++.
refactor mruby method(fix indent. remove temporary value, duplicate procedure)
revert mrb_equal method
Merge pull request #2538 from kkkkkt/refactor-method

refactor mruby method(fix indent. remove temporary value etc)
Fix error handlings in mirb.

mrb_parser_new() and mrb_generate_code() may return NULL.
Merge pull request #2539 from cubicdaiya/issues/mirb_error_handlings

Fix error handlings in mirb.
Fix error hanldlings in read_irep_record().

read_irep_record_1() and read_irep_record() may return NULL.
Fix error handling for mrb_generate_code().

The return value of mrb_generate_code()
must be null-checked before referencing.