Fix the search for matching timestamps in the GPS correlator. Timestamps...

Fix the search for matching timestamps in the GPS correlator. Timestamps before an item were not found if two or more items were between two GPS timestamps, leading to only the first item being correlated, both in interpolation mode and in normal mode.

This should also be the cause for bug 273520, please check whether it is now fixed as well.

CCBUG: 273520
CCMAIL: photonoxx@free.fr