Fix build on ARMv8 64bit.

I previously used the wrong variable (_ARCH64EL_ instead of
__ARCH64EL__).

BUG=33
Fix warnings.
Update Changelog.
fix bad merge.
Backport most of the SConstruct improvements.

Contrary to v2.0, v1.1 we don't have shared libraries for v1.1.
Update changelog.
Enable shared libraries in v1.1 branch.
Update Changelog.
Add packaging/, that allows for a folly SRPM to be created

The SRPM can be built, as long as the double-converion-devel RPM is
installed. The change include a spec file for the SRPM, and a bash
script that can run on a Fedora-system to generate the srpm in
a user-provided directory.

For example:

    ./packaging/build-srpm -o .

Will generate an SRPM in the local directory, for example:

    double-conversion-1.1.5.date2014.01.17.164630.gite33f459-1.fc19.src.rpm