Time to back-patch libxml deprecation fixes?

I just noticed that my animal indri has been failing in the
back branches since I updated its MacPorts packages a few
days ago:

ccache gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Werror=unguarded-availability-new -Wendif-labels -Wmissing-format-attribute -Wcast-function-type -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -Wno-compound-token-split-by-macro -g -O2 -fno-common -Werror -fvisibility=hidden -I. -I. -I../../src/include -I/opt/local/include -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.4.sdk -I/opt/local/include/libxml2 -I/opt/local/include -I/opt/local/include -I/opt/local/include -I/opt/local/include -c -o mbuf.o mbuf.c
xpath.c:77:2: error: 'xmlSubstituteEntitiesDefault' is deprecated [-Werror,-Wdeprecated-declarations]
xmlSubstituteEntitiesDefault(1);
^
/opt/local/include/libxml2/libxml/parser.h:952:1: note: 'xmlSubstituteEntitiesDefault' has been explicitly marked deprecated here
XML_DEPRECATED XMLPUBFUN int
^
/opt/local/include/libxml2/libxml/xmlversion.h:447:43: note: expanded from macro 'XML_DEPRECATED'
# define XML_DEPRECATED __attribute__((deprecated))
^
1 error generated.
make[1]: *** [xpath.o] Error 1

I could switch the animal to use -Wno-deprecated-declarations in the
back branches, but I'd rather not. I think the right answer is to
back-patch Michael's 65c5864d7 (xml2: Replace deprecated routines with
recommended ones). We speculated about that at the time (see e.g.,
400928b83) but didn't pull the trigger. I think 65c5864d7 has now
baked long enough that it'd be safe to back-patch.

regards, tom lane