Libsoc depends on libxml2, but libxml2-2.7.6 is not sufficient

[rfaelens]

Libsoc should check for libxml2-devel > 2.8, as previous versions do not have the xmlXPathNodeEval function.

[rikardn]

Thanks for pointing this out. How did you find out which version was needed?

I did objdump -TC libxml2.so | grep xmlXPathNodeEval

And got version 2.9.1

I don't know if this is too new to depend on. There might be other functions to use in that case. Otherwise I will just add a check for that version.

[rfaelens]

Based on the news.html in libxml2 source tree, this is only available from version 2.9.1 onwards.