mysql: fix install into DESTDIR

this is a regression from the version bump, now it needs a different
syntax to make mysql respect DESTDIR.
mysql: build without 180 MB of tests
mysql: bump to 5.6.13
Merge branch 'master' into newpkg2
Revert "Merge branch 'master' into newpkg2"

This reverts commit 44beead488bc14dd2bc9ad5d76ea84b2f1542e01, reversing
changes made to 6af54774c18d812ebc5a5df1b8aa3a07822d1e76.
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