Merge pull request #2154 from cremno/dbl_dig

remove `DBL_DIG` fallback definition
Merge pull request #2157 from cremno/remove-mrb_str_offset

remove `mrb_str_offset`
Merge pull request #2155 from cremno/define-resize_capa-as-a-function

define `resize_capa` as a function
Merge pull request #2156 from cremno/fix-disabled-stdio-2

fix disabled stdio
turn on MRB_GC_STRESS for debug build on travis
Add doubling stack extend, as fix for #2016
Merge pull request #2147 from take-cheeze/dump_line_file

Print file name and line number in codedump if available.
Merge pull request #2158 from kyab/support_doubling_stack

Add doubling stack extend, as fix for #2016
codedump for binary mrb files as well
indent codedump when file/line info is not available; ref #2147
Support local variables information dumping.
Implement Kernel.local_variables for testing dumped local variables information.
Remove `lv_len` and use `nlocals - 1` instead.
Check that `lv`'s length is always `nlocals - 1`.
adjust indent
remove trailing spaces
Merge pull request #2160 from nobu/space

Space
use Kernel#__send__ insteard of Kernel#send
Implement Struct#to_h .
Added dump_irep in header.
Merge pull request #2162 from ksss/__send__

use Kernel#__send__ insteard of Kernel#send