Wrapping the SHLINKFLAGS in an array rather than as a single string
caused the link flags to be passed to clang double quoted. This cuased
clang to interpret the flags as a string rather than as a flag which
caused the -install_name flag to never be passed to the linker.

This actually is only for OS X. On linux ldconfig must be run after
installing in order to update the library cache. Need to look into how
to get scons to do this for the user.

Set the proper path for the shared library so that anything linking
against it will be able to find the library.

Go, and likely other language bindings will, need access to create
new combinators. This functionality is currently located
src/parsers/parser_internal.h. Install this header to the system with
dependent headers until a better solution can be found.

Create a pkg-config file and install it to $prefix/lib/pkgconfig

Don't pass the entire environment to SCons. Only pass the PATH

Don't clober the Environment (and thus the ENV['PATH'] by redefining it
and don't link against lr by default. Only add it if uname is not Darwin