Support out of tree builds with autotools build system

[mstewartgallus]

Mercury should support out of tree builds with the autotools build system where the build is separate from the source tree. The first issue I could see blocking this is that on line 204 of configure.ac there is the command . ./VERSION. This should be replaced by something like . "${srcdir}/VERSION". I am using the 13.05.1 release.

[PaulBone]

Thanks Steven

This is a feature that I've wanted for a while, so I certainly agree that it
should be there and we should make some effort. Thanks for taking a quick
look but I suspect it will take a lot of work to make this happen. I'll
leave the ticket open and hopefully someone will have the time to work on
this.

Thanks.

[juliensf]

Actually, the first issue will be line 103, which contains:

AC_PREFIX_DEFAULT(/usr/local/mercury-. ./VERSION; echo $VERSION)

This is more problematic than the instance at line 204 because at that point in the
generated configure script the srcdir variable is not defined.