Overflow in Connection TTL

There is a possibility of an overflow at https://github.com/apache/httpcore/blob/4.4.x/httpcore/src/main/java/org/apache/http/pool/PoolEntry.java#L88 when calculating the validity deadline. When Long.MAX_VALUE (or values sufficiently close to it) is used as the TTL it results in a negative validity deadline which causes every connection to be single use. This is very surprising behavior and may not be immediately obvious in test environments.