MFC r249488:

Similarly to proc_getargv() and proc_getenvv(), export proc_getauxv()
to be able to reuse the code.
MFC r250116:

Make an attempt to detect missing MTREE files in distrib-dirs.  Not
perfect, but this is just a developer seatbelt

PR:		conf/176897
Submitted by:	Garrett Cooper <yaneurabeya@gmail.com>