Fix compile warning for abort
Merge pull request #1290 from kyab/fix_abort_warning

Fix compile warning for abort() when MRB_GC_STRESS is defined
make mrb_str_new_cstr DRY

Using str_new eliminates duplicated codes in mrb_str_new_cstr.
Merge pull request #1292 from cubicdaiya/dry_mrb_str_new_cstr

make mrb_str_new_cstr DRY
Cleanup mrb_str_resize().
Merge pull request #1293 from monaka/pr-cleanup-mrb_str_resize

Cleanup mrb_str_resize().
Improve target example to more practical.
Add fallback for allocate CRC buffer
Merge pull request #1295 from kyab/improve-target-example

Improve target example to more practical.
Merge pull request #1296 from kyab/fallback-for-crc-buffer

Add fallback for allocate CRC buffer
fixed a bug in push back list; close #1298
Merge branch 'master' of github.com:mruby/mruby
Fix crash on load *mrb
Merge pull request #1303 from kyab/sirep_fix2

Fix crash on load *mrb
add mrb_malloc_simple() that returns NULL on error
use mrb_malloc_simple() to allocate crc buffer; close #1302