gdb/testsuite/
* gdb.base/catch-syscall.c: Make unreferenced statics non-static to
ensure clang would not discard them.
* gdb.base/gdbvars.c: Ditto.
* gdb.base/memattr.c: Ditto.
* gdb.base/whatis.c: Ditto.
* gdb.python/py-prettyprint.c: Ditto.
* gdb.trace/actions.c: Ditto.
* gdb.cp/ptype-cv-cp.cc: Mark unused global const int as used to
ensure clang would not discard it.
Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.