Resources are loaded from the current working directory. By setting the
current working directory to the source dir, rather than the out of tree
build dir, we can easily pick up the original resources without copying
them around during configuration.

Fixed typo

Meson is a build system somewhat like cmake, but without all of the
rough edges. It supports many OSes, including all of the major ones, and
a large number of C++ compilers.

My interest isn't really in convincing people to use meson as the
default here, but meson provides a subproject mechanism that can fetch
external projects and build them along with the main project in a single
configure/compile invocation. This is extremely useful for platforms
that lack a (competent) package manager.

As far as I know the meson build does everything the cmake build does,
with one exception: generate the cmake config/version files. meson can
generate these files, but only in simple cases, and not when using
export targets like tinyxml2 does.