blkid: split SONAME and LIBBLKID_VERSION

blkid: split SONAME and LIBBLKID_VERSION

It seems better to split SONAME and the public library version. The
library version will be the same as util-linux-ng PACKAGE_VERSION.

PACKAGE_VERSION:               <maj>.<min>[-<suffix>]  e.g. 2.15-rc2
Symbols versioning:            BLKID_<maj>.<min>       e.g. BLKID_2.15
blkid_get_library_version():   <maj>.<min>.0           e.g. 2.15.0
SONAME:                        libblkid.so.1

See also the original patch a0487b1cb5beffb8f6783476664b01e8833e0ea8
where was introduced library versioning.

Signed-off-by: Karel Zak <kzak@redhat.com>