via ABUILD_LOG_CMD config option

This is supposed to be used on the build servers

fixes regression

so we dont leak functions like 'build' and other variables.

syslinux switched to elf format from 5.0

This is an alternative to saveas-*:// which should be slightly more
intuitive. It also is similar to what arch linux does.

This has the nice effect that we get the index automatically built for
our REPODEST.

Discussion here:
http://lists.alpinelinux.org/alpine-devel/0249.html

fixes #1477

ref #1537

Tool to help find ABI breakages in package upgrades

ref #1484

- remove duplicate provides with so version 0
- exit with error if there are multiple provides with different versions

It is never and should never be used.

So far only openjdk6 needs it and uclibc cannot have it, so we make
it optional.

This will hopefully help detect depends problems early