Add shebang line to a2server-aliases

FWIW the reason why I keep adding shebang lines to these scripts that
get sourced (and therefore don't need them) is that it alerts a few text
editors that offer syntax highlighting based on magic numbers in files
that they are in fact bash scripts and contain bashisms that shouldn't
be flagged as errors in strict bourne shells.

scripts/a2server-aliases.txt

@@ -1,3 +1,4 @@
+#! /bin/bash
 # A2SERVER aliases: