assembly plugin should use posix, not gnu for tarLongFileMode

<tarLongFileMode>gnu</tarLongFileMode> causes some issues on some platforms. Most modern versions of tar support the newer posix mode, which supports all the features gnu does, plus more.

Instead of the release profile's execution of the source-release-assembly using the above setting, that should be removed from the assembly configuration, and instead, the parent pom should add the following to the <properties>:

<assembly.tarLongFileMode>posix</assembly.tarLongFileMode>