The library is already available on extras-devel (package name is "libsdl-gles1.2-dev", garage project is "sdlhildon"). For now, best documentation is
Unpacking libsdl-gles1.2-1 (from .../libsdl-gles1.2-1_1.0.0_armel.deb) ... dpkg: error processing /var/cache/apt/archives/libsdl-gles1.2-1_1.0.0_armel.deb (--unpack): trying to overwrite `/opt', which is also in package espeak-data Selecting previously deselected package libsdl-gles1.2-dev.