Import obstack.c and obstack.h am: 61a263b27f am: 41994c0bcc am: 4a4da698d4 am: 8fc20ccd25 am: 0ca822ead0

Original change: https://android-review.googlesource.com/c/platform/external/obstack/+/1843833

Change-Id: I8d2881e9708a73e983fa4c006129e9255bcde67a
tree: 4bf158aad52e1579720839f76306df099af3144e
  1. include/
  2. libiberty/