Adjust some indents

cleanup: unused variable local_svar

Remove trailing whitespaces. This is just a cosmetic change.

bugfix: assert_raise

Remove unused var sv

Fix two typos

format some source code (vm.c)

Should be MRB_DATA class. RStruct isn't managed by mruby core. So it should be self-managed class instances.

Remove unused struct and more

format some source code (class.c)

Use typedef names as possible

Fix arena size check.