5.2 compatibility with 5.1?

Hi,

I installed 5.2-RC1 and wanted to run my Emacs binary from the 5.1
system.

However, 5.2-RC1 has libutil.so.4 while 5.1 had libutil.so.3.  This was
of course easy to workaround by symlinking libutil.so.3 from 5.1 into
5.2-RC1.

More serious seems the following problem: Sometimes when sending Email
from Evolution built on 5.1, running on 5.2-RC1, Evolution crashes
with an undefined reference from libc_r:

/usr/libexec/ld-elf.so.1: /usr/X11R6/lib/evolution/1.4/libeutil.so.0:
Undefined symbol "gethostbyaddr_r"

Indeed gethostbyaddr_r seems to be present in libc.so on 5.1, but not
any more in 5.2-RC1.

I thought minor number upgrades would have compatible libs?
Do we need a compat51 package?

If libc was modified in an incompatible way, shouldn't we bump the
version number?

--
Regards,
Georg.