BUG #12275: configure incorrectly tests libxml2 version

The following bug has been logged on the website:

Bug reference: 12275
Logged by: Greg Davidson
Email address: greg(dot)davidson(at)gmail(dot)com
PostgreSQL version: 9.4.0
Operating system: mint 17.1
Description:

I had to comment out the libxml2 version check to get 9.4.0 to build.
Perhaps it's because of the suffix on the version number?
$ ./configure --with-libxml --with-libxslt --enable-debug --enable-cassert
\
--with-tcl --with-tclconfig=/usr/lib/tcl8.6 --prefix=/usr/local/pgsql-9.4.0
...
checking for xmlSaveToBuffer in -lxml2... no
configure: error: library 'xml2' (version >= 2.6.23) is required for XML
support

$ dpkg-query -l '*xml2*'
||/ Name Version Arch Description
+++-==================-=======================-======-===========================================
ii libxml2:amd64 2.9.1+dfsg1-3ubuntu4.4 amd64 GNOME XML library
ii libxml2:i386 2.9.1+dfsg1-3ubuntu4.4 i386 GNOME XML library
ii libxml2-dev:amd64 2.9.1+dfsg1-3ubuntu4.4 amd64 Development files for
the GNOME XML library
ii libxml2-doc 2.9.1+dfsg1-3ubuntu4.4 all Documentation for the
GNOME XML library
ii libxml2-utils 2.9.1+dfsg1-3ubuntu4.4 amd64 XML utilities

P.S. I hope that the appearance of line clipping I'm seeing above is an
illusion. Perhaps the bug report textentry widget should have room for 80
character wide pastes from terminals?