MFC r262810, r262862, r264105:
r262810:
  Merge enabling building FreeBSD/arm images as part of the
  release build process.

r262862:
  Provide backwards-compatibility with release.conf SVNROOT
  entries that do not have a trailing '/'.

r264105:
  Add ZEDBOARD support for release builds.

* Local modifications:
  - Set SRCBRANCH from head/ to stable/10/.
  - Strip svn:merginfo from ^/projects/release-embedded to avoid
    pollution.

Sponsored by:	The FreeBSD Foundation