Merge topic 'minor-cleanups'

6c3dfd25 CommandLineArguments: initialize internal class members directly
a93bc28c SystemTools: Drop unnecessary .c_str()
6e36d909 SystemTools: Reduce scope of 'buf' variable in CollapseFullPath
31f5cdeb RegularExpression: Initialize private members on construction
116a4919 RegularExpression: Reduce scope of 'len' variable

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !143