Project and library version are now stored in
version.txt and libtool_version_info.txt files respectively.
Both autotools and meson get their versioning information from this files.
Meson additionally automatically transforms library version
from libtool's own format.
Also raise meson version requirement from 0.47 to 0.57 which
is required by these changes.
Tim Rühsen
Alexey Rochev