[regression] Filtering doesn't work if a lone @ is found in a line to interpolate

If you try to filter a file containing say :

${project.artifactId} @ ${project.version}

It'll be rendered as 'foo @ ${project.version}', when you expect 'foo @ 1.0.0'

This used to work in maven-war-plugin <= 2.3, so I suspect this is caused by the upgrade to maven-filtering:1.1.

Note that this bug has affected filtering using maven-resource-plugin for quite some time now, so the root cause is definitely somewhere in the filtering component. Opening the bug here to keep track of the regression in m-w-p