v5.3

This is functionally the same as the tagged version cMsg-5.2 with the exception that the explicit "throw" clauses in method declarations have been removed to make it compatible with modern compilers.

Note that previous releases were made by simply tagging them. For example the tag cMsg-5.2 contains the cMsg 5.2 "release". By moving to the release feature of GitHub it was decided to switch to a version naming scheme that is more consistent with other JeffersonLab packages' naming schemes.