package/gpsd: bump version to 3.20

package/gpsd: bump version to 3.20

Removes BR2_PACKAGE_GPSD_PPS config option, since PPS functionality is
no longer optional and always enabled in gpsd's SCons configuration.

Removed passing ntpshm=y to SCons since that feature is also no longer
optional.

Added a patch adapted from changes merged upstream post-3.20 to fix a
build failure during cross-compilation when checking sizeof(time_t)
and where shared libraries were being linked with ld rather than g++.

Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>