DatabaseExperiment: add register FI

Calling the DatabaseCampaign with --inject-registers or
--force-inject-registers now injects into CPU registers.  This is achieved
by reinterpreting data addresses in the DB as addresses within the register
file.  (The mapping between registers and data addresses is implemented in
core/util/llvmdisassembler/LLVMtoFailTranslator.hpp.)  The difference
between --inject-registers and --force-inject-registers is what the
experiment does when a data address is not interpretable as a register: the
former option then injects into memory (DatabaseCampaignMessage,
RegisterInjectionMode AUTO), the latter skips the injection altogether
(FORCE).

Currently only compiles together with the Bochs backend; the
DatabaseExperiment's redecodeCurrentInstruction() function must be
moved into the Bochs EEA to remedy this.

Change-Id: I23f152ac0adf4cb6fbe82377ac871e654263fe57

src/core/comm/DatabaseCampaignMessage.proto.in

@@ -23,6 +23,12 @@ message DatabaseCampaignMessage {
     required InjectionPointMessage injection_point	= 10 [(sql_ignore) = true];
 
     required bool inject_bursts				= 11 [default = false];
+    enum RegisterInjectionMode {
+        OFF = 0;
+        AUTO = 1;
+        FORCE = 2;
+    }
+    optional RegisterInjectionMode register_injection_mode = 12 [default = OFF];
 }
 
 message DatabaseExperimentMessage {