pkg-config: egl.pc: hardcode version to 7.10 to make weston happy

weston requires version 7.10, since it's most of the time
compiled against mesa.

In weston/configure.ac, there's something like:
  if test x$enable_egl = xyes; then
      AC_DEFINE([ENABLE_EGL], [1], [Build Weston with EGL support])
      COMPOSITOR_MODULES="$COMPOSITOR_MODULES egl >= 7.10 glesv2"
  fi

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
pkg-config: glesv2.pc: remove un-needed .private fields

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
pkg-config: add wayland-egl.pc

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>