Overhaul Linux/Unix packaging system, primarily to avoid conflicts with vendor-suppli...

Overhaul Linux/Unix packaging system, primarily to avoid conflicts with vendor-supplied libjpeg-turbo packages (such as in Fedora and RHEL 6.)  This also streamlines the packaging system somewhat, since it is no longer necessary to move the TurboJPEG libraries into the system library directory.  Relocating those libraries was originally done to provide backward compatibility with TurboJPEG/IPP, but that package is long obsolete, and the software that formerly used it has been linking statically with libjpeg-turbo for quite some time.

If the default prefix (/opt/libjpeg-turbo) is used, then we now always install 32-bit libraries in /opt/libjpeg-turbo/lib32 and 64-bit libraries in /opt/libjpeg-turbo/lib64 instead of trying to conform to the Debian or Red Hat conventions.  The RPM and DEB packages will now be created with the directory structure defined by the configure variables "prefix", "bindir", "libdir", etc., with the exception that the docs are always installed under /usr/share/doc/{package_name}-{version}.

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@944 632fc199-4ca6-4c93-a231-07263d6284db