hwloc.h: minor fixes in comments

(cherry picked from commit 12f229df95b10e16927faa137654f093aaec09a0)
Add support for the renaming of Socket into Package in future releases.

HWLOC_OBJ_PACKAGE and "Package" strings are mapped to the socket type
so that XMLs etc generated with v2.0+ can be imported in v1.10.1.