src/version.sh should explicitely declare to use bash

[Clint Adams]

> VERSION=$(grep define.VERSION config.h | awk '{print $3}' | tr -d '"')
> 
> I believe the above statement isn't valid in sh, but it's one of the
> extensions by bash. Thus the first line of the script should be
> "#!bin/bash", not "#!/bin/sh". Actually, after changing the line as such,
> the entire compilation finished without any errors.
> 
> So, I think the script shoud explicitly declare to use bash, not sh. 

This is due to Sun refusing for over a decade to use a POSIX-conformant
shell as /bin/sh.  Solaris's /bin/sh supports the obsolete backtick form
of command substitution, and Solaris's /usr/xpg4/bin/sh (a/k/a ksh)
supports the recommended $() form.

A build dependency on bash is probably not a good idea.