`a` in `a.m += c` or `a[b] += c` should be evaluated only once.

Add missing regs update

mrb_vm_define_class() may realloc() mrb->c->stack because it calls
mrb_funcall() for inherited hook. If mrb->c->stack is realloc()-ed, regs
refers orphan address.

deprecate and fix VS2010/2012 build

They don't have <inttypes.h>, only <stdint.h>.

Fix doesn't work bintest on :visualcpp toolchain

Added example for cross-compiling on Intel Edison

Add appveyor.yml

Reduce compiler include_paths

Add default benchmark build config

Fix SEGV by backtrace and GC

Suppress a warning

GitHub: fix #3122

It reverts #3126. #3126 fixes the segmentation fault but generates
broken backtrace.

This change fixes the segmentation fault and generates correct
backtrace. The strategy of this change is "generating backtrace while
irep is alive".

/tmp/test.rb:
    def gen
      e0 = nil
      begin
        1.times {
          raise 'foobar'
        }
      rescue => e
        e0 = e
      end
      e0
    end

    e = gen
    GC.start
    gen
    GC.start

    puts e.backtrace.join("\n")

Run:

    % bin/mruby /tmp/test.rb
    /tmp/test.rb:5:in Object.gen
    /home/kou/work/ruby/mruby.kou/mrblib/numeric.rb:77:in Integral#times
    /tmp/test.rb:4:in Object.gen
    /tmp/test.rb:13

FYI:

    % ruby -v /tmp/test.rb
    ruby 2.3.0p0 (2015-12-25) [x86_64-linux-gnu]
    /tmp/test.rb:5:in `block in gen'
    /tmp/test.rb:4:in `times'
    /tmp/test.rb:4:in `gen'
    /tmp/test.rb:13:in `<main>'

This reverts commit bf7719fe, reversing
changes made to 4f4fa0ad.

We should get backtrace while irep is alive.

    mrbgems/mruby-eval/src/eval.c: In function ‘create_proc_from_string’:
    mrbgems/mruby-eval/src/eval.c:152:10: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
         file = "(eval)";
              ^

Null check for irep & initialize loc.lineno