#21 Use PKG_CHECK_MODULES to find libxml2 and lib(e)xslt

[Hugh McMaster]

Debian is removing xml2-config and xslt-config in favour of pkg-config. This means XMLStarlet fails to build from source.

I've patched configure.ac to use the PKG_CHECK_MODULES pkg-config macro to find libxml2 and libxslt. If available, libexslt is preferred over libxslt (the main difference being the addition of -lexslt).

[Tomasz Kłoczko]

Is it possible to merge this patch?