Compare the content of PM_ASN_SET in path masks. A reconfiguration
was not properly triggering a reload of affected protocols when the
members of a set in a path mask change.
Also, update the printing code to so that it can display sets in a path
mask.
Add a missing return statement. Path masks with the same length were all
considered the same. Comparing two with different length would cause
out-of-bounds memory access.
Implement regex-like '+' operator in BGP path masks to match previous
path mask item multiple times. This is useful as ASNs may appear
multiple times in paths due to path prepending for traffic engineering
purposes.
