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

Distinguish the cases when a dup symbol is in different versions
(evil, needs a error) or in the same version (harmless, deserves
a mere warning).

Noticed by: grehan@, tinderbox

MFp4:

- Check for duplicated symbols and suggest moving them to ObsoleteVersions.
- Improve and unify error handling.
- Make the regular expressions more uniform, robust, and less sensitive
to harmless variations in the input such as those to whitespace amount.

Reviewed by: deischen
Tested with: md5 (Version.map files in /usr/obj stay the same)

Put local symbol suppression rule into most recent (e.g. last) version
block.

Approved by: re (kensmith)

When generating the version map file, order versions oldest
first to make it easier for rtld to choose the oldest version
of a symbol.

Sumbitted by: kan

Teach bsd.lib.mk to auto generate a version map file based on
a set of symbol definitions (VERSION_DEF) and symbol mappings
(SYMBOL_MAPS).

Add an awk script to generate the version map.

Suggested by: ru
Helped by: ru
Reviewed by: ru