rapidxml: add patch to fix usage with gcc 4.7+

The official `rapidxml` package release only supports up to GCC 4.6.x
for all capabilities. Implementers attempting to include the file
"rapidxml_print.hpp" will all result in a compilation failure when using
a currently supported Buildroot GCC version (all 4.7+ at this time).
With the provided patch, dependent packages will be able to use all of
rapidxml's capabilities using a generated toolchain from Buildroot (let
alone external toolchains).

Signed-off-by: James Knight <james.knight@rockwellcollins.com>
[Thomas: rework patch so that it contains the proper line endings, and
applies properly without a pre-patch hook to convert the line endings
beforehand.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>