I\'ve gone to http://sourceforge.net/project/showfiles.php?group_id=2435, downloaded the Automated MinGW Installer for MinGW 5.1.4 and at the same time the GNU Source-Level
You can safely overwrite the files prepackaged with MinGW with the (newer) ones from the gdb tarball. You can also choose not to overwrite them - just make sure to pick either one set, i.e. avoid mixing files from the older and the newer package.
Most of the offending files are probably not really relevant to you anyway. For example, the files belonging to the libbfd library aren't required for gdb's day to day operation, they're used if you want to extend the debugger or write debugging tools yourself.
At any rate, make a backup of the mingw directory before untarring the new release. It's very easy since MinGW is self-contained in that directory. That way, if anything should malfunction, you can just delete the directory and restore from the backup.