package/sdl2_ttf: fix detection of OpenGL

package/sdl2_ttf: fix detection of OpenGL

Backport a opatch from upstream to preoperly detect OpenGL, add patch to
fix autoreconf.

Fixes:
    http://autobuild.buildroot.org/results/be9/be9d9d0d75dca62d9edb28c1e4d81f7f33b30ea8/
    http://autobuild.buildroot.org/results/db8/db87a00a7cd1f8d1627fa4a39a0f67e9328b2b0f/
    http://autobuild.buildroot.org/results/f45/f45a9588090c296c9c5ece2cbc71f8bb64bebf73/
    http://autobuild.buildroot.org/results/9cb/9cb669ab6760420421e3c907462b69fe36c46601/
    and many others...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Peter Thompson <peter.macleod.thompson@gmail.com>
Cc: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>