Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add missing `void' keyword.

- Simplify the procedure of retrieving XML-data from the kernel.
- Fix a number of potential memory leaks in libgeom related to doing realloc
without freeing old pointer if things go wrong.
- Fix a number of places in libgeom where malloc and calloc return values
were not checked.
- Check malloc return value and provide sufficient warning messages when XML
parsing fails.

PR: kern/83464
Submitted by: Dan Lukes <dan - at - obluda.cz>
Approved by: kib (mentor)

Second call of sysctl() is used to gather a proper size of a memory chunk
needed to hold the GEOM tree. At this point, pointer 'p' has an improper
value (as it was used previously), and we're getting EFAULT. Fix this
functionality by passing NULL instead of 'p'.

This fixes mdconfig(8) -l output with high number of md(4) devices.

Found by: kris
Reviewed by: phk

Leak more stuff into libgeom.