[xml] libxml2.so and -lpthread

[Weiqi Gao <weiqigao networkusa net>]

While trying to update libxml2 and libxslt to the latest release 2.4.10
and 1.0.7, I encountered the following problem:

If I specify '--with-threads' for libxml2, then the subsequent build of
libxslt fails with the linker complaining about undefined references to
some pthread_* symbols.

Adding '-lpthread' to the linker command for libxml2.so fixes the
problem.

-- 
Weiqi Gao
weiqigao networkusa net