wrap: add user agent when downloading files
wrap: add user agent when downloading files

This lets servers know when they're being used by meson. It also avoids
issues where the Independent JPEG Group decided to ban the
"Python-urllib" default user agent.

Fixes https://github.com/mesonbuild/libjpeg/issues/9

mesonbuild/meson,becm/meson,becm/meson,pexip/meson,becm/meson,jpakkane/meson,pexip/meson,jpakkane/meson,pexip/meson,jpakkane/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,becm/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,jpakkane/meson,becm/meson,jpakkane/meson,becm/meson,becm/meson,mesonbuild/meson,jpakkane/meson,becm/meson,pexip/meson,jpakkane/meson,becm/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,pexip/meson,pexip/meson,pexip/meson,mesonbuild/meson,becm/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,pexip/meson,jpakkane/meson