ECL 8.12

This release is the last one before a major redesign of ECL, which will affect
issues like Unicode streams and handling of interrupts.

This is also the first one to follow the new numbering scheme, inspired by that
of Ubuntu. The release number follows the scheme year.month.[0-9], where the
last digit marks the patch release. The numbering is now incorporated in the
library names, so that different versions of ECL may coexit on the same system.