dash: bump to version 0.5.7-3

Bump to patchlevel 3 since 2 is gone upstream, fixes when
sources.buildroot.net isn't available:
http://autobuild.buildroot.net/results/5ee/5ee6544a9d08025060cb5806870ae1c3f252cd93/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>