upgrade-libc6

As new mainline kernels are released, their kernel headers require greater versions of GLIBC which are not available from the default repositories on older Ubuntu versions.

To overcome that, configure.sh script generates:

• upgrade.sh that upgrades libc6 and depending packages to the latest versions from one of the newer repositories,
• downgrade.sh that downgrades all versions to what was previously found in the system.

Disclaimer: messing up the libc-bin and locales packages will make your system corrupt, as a great number of programs depends on the C common libraries - use at your own risk.