Building libsaxsdocument with XML fails on Windows

[chrisemblhh]

(Proximate cause: upgraded CMake has better search heuristics, so it finds the libxml2 library and tries to build with canSAS-XML enabled, whereas previously libxml2 was not found and canSAS was disabled.)

Trying to build saxsview gives linker errors saying something like: undefined reference to '__imp_recv'

[chrisemblhh]

Here are some links to related problems elsewhere:
https://mail.gnome.org/archives/xml/2009-November/msg00005.html
https://github.com/rwinlib/libxml2
http://www.pokorra.de/coding/compile_libxml_mingw.html

[chrisemblhh]

Manually changing the value of LIBXML_LIBRARIES in the CMake GUI from "C:/[PATH]/libxml2.a" to "C:/[PATH]/libxml2.lib" fixes the linker error but will add a runtime dependency on libxml2.dll