Define debuggerd class, permissions, and rules.

Define a new class, permissions, and rules for the debuggerd
SELinux MAC checks.

Used by Ib317564e54e07cc21f259e75124b762ad17c6e16 for debuggerd.

Change-Id: I8e120d319512ff207ed22ed87cde4e0432a13dda
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>