make osm_elements a loop variable, not a local variable
make osm_elements a loop variable, not a local variable

The vector osm_elements was created and destroyed in each loop
iteration. It can be kept and cleared instead.

bjtaylor1/osrm-backend,Project-OSRM/osrm-backend,neilbu/osrm-backend,neilbu/osrm-backend,raymond0/osrm-backend,raymond0/osrm-backend,yuryleb/osrm-backend,felixguendling/osrm-backend,oxidase/osrm-backend,neilbu/osrm-backend,Project-OSRM/osrm-backend,oxidase/osrm-backend,duizendnegen/osrm-backend,duizendnegen/osrm-backend,yuryleb/osrm-backend,bjtaylor1/osrm-backend,Project-OSRM/osrm-backend,duizendnegen/osrm-backend,frodrigo/osrm-backend,bjtaylor1/osrm-backend,felixguendling/osrm-backend,yuryleb/osrm-backend,yuryleb/osrm-backend,raymond0/osrm-backend,duizendnegen/osrm-backend,raymond0/osrm-backend,frodrigo/osrm-backend,deniskoronchik/osrm-backend,deniskoronchik/osrm-backend,deniskoronchik/osrm-backend,oxidase/osrm-backend,felixguendling/osrm-backend,KnockSoftware/osrm-backend,Project-OSRM/osrm-backend,KnockSoftware/osrm-backend,frodrigo/osrm-backend,frodrigo/osrm-backend,deniskoronchik/osrm-backend,KnockSoftware/osrm-backend,oxidase/osrm-backend,bjtaylor1/osrm-backend,KnockSoftware/osrm-backend,neilbu/osrm-backend