#471: @SneakyThrows should work in NetBeans

This patch tries to fix @SneakyThrows in NetBeans. Conceptually, it has two parts:
-first, the catch param's parameter is marked as Flags.PARAMETER, which means the maker will set a position to it. Without this change, (nb-)javac's Flow crashes while trying to analyze the augmented source.
-second, the try statement, and the try block are granted both starting and ending position. This is needed, as NetBeans often uses the span (start+end position) to quickly find the tree (and path from the root to the tree) that are at a given position, and it was ignoring the try statement, as it did not have any positions.

The JDK 8 branch in Javac that resolves the storeEnd method is written in a way that allows it to work in both NetBeans 7.4 and the current trunk builds (NetBeans 8.0).

Please let me know if any changes are desired.