dynamicCode should use polling instead of re-checking only once

Functionality to add/problem to solve

db/dynamicLibrary/dynamicCode/dynamicCode.C in parallel can have that the library does not exist on all slave processors. It first checks at beginning and then waits 'fileModificationSkew' seconds and rechecks. If this fails the code will fail. Nicer if the check gets done multiple times before failing.

Alternatively send over the library (is this possible? is it cross-node compatible?)