configure.ac: don't add RPATH when searching for extra libs

Closes #766
doesn't appear to actually be required, and adding RPATH breaks Debian and OpenSUSE policy
all flames to me
Merge remote-tracking branch 'upstream/master'
Expand abbreviations at the beginning of commands as discussed in https://github.com/fish-shell/fish-shell/issues/731
Fix "command not found" handler behaviour.
Fix tabs in share/functions/__fish_config_interactive.fish
Merge remote-tracking branch 'upstream/master'