Allow SMARTS expressions of the form [h0] and [!h0] analogous to [H0] and [!H0]. Previously this was not possible to null handling semantics.
Merge branch 'master' of github.com:cdk/cdk
Unit tests for bug reports by Yannick on the cdk-user@ mailing list

Change-Id: I20cdb8e7f9c0c25be4fbcf344e3dddfaf4e93794
Signed-off-by: John May <john.wilkinsonmay@gmail.com>