Find Corrade _before_ checking for its configuration.
Platform: added WindowlessNaClApplication.

Stripped-down version of NaClApplication with unusable default
framebuffer and no event handling, primarily for various testing usage.
Platform: Doxygen fixes.
Platform: portable WindowlessApplication usage in `magnum-info`.
FindMagnum.cmake: removed duplicate code.
Platform: ported magnum-info to NaCl.

The binary installs into `bin/`, the HTML and NMF into `share/`, the
user is currently expected to copy them manually to server.
Strip binaries in NaCl's PKGBUILD.

Saves 10 MB.
Platform: added CORRADE_GCC47_COMPATIBILITY to `magnum-info`.
Platform: print each flag on separate line in `magnum-info`.

It's more readable.
Platform: added also CORRADE_TARGET_EMSCRIPTEN to `magnum-info`.