logcat: Minor fixes

Remove -r default value implementation (since is not functional).
Check the status of some memory allocations.
Make sure that the pruning buffer is set to NULL if we get to the end of  the loop.
Make sure that the file status is successfully retrieved before using the size.
Add strtouia - string to unsigned argument.
Add logcat_panic with/without printing an error message and help.
Play nicer with the android namespace.

Change-Id: Id4c37cf64968128424e29bf1725f6c9a5924a0e2
Signed-off-by: Traian Schiau <traianx.schiau@intel.com>