Preparing SSA support for SEA IR: reaching definitions.

Added the following:
- Downward-exposed uses.
- Reaching definitions.
- Better .dot generation.

Per file:
sea_ir/sea.*: Downward exposed definitions and reaching definitions code.
dex_instruction.*: Wrapper function added to expose the vA register,
                   which is later used by dataflow analysis.
sea_ir/instruction_tools.*: These tools provide info needed by dataflow analysis
                            that is dependent on dex format.
dex/frontend.cc: Formatting issues fixed.
sea_ir/*.*: All files pass cpplint validation.
*.mk: Support for new files added in this CL.

Change-Id: Ic510e7fb55aebcde99a121304ee7e841a3307358
diff --git a/src/dex_instruction.h b/src/dex_instruction.h
index 602667a..0407c57 100644
--- a/src/dex_instruction.h
+++ b/src/dex_instruction.h
@@ -215,6 +215,7 @@
   }
 
   // VRegA
+  int32_t VRegA() const;
   int8_t VRegA_10t() const;
   uint8_t VRegA_10x() const;
   uint4_t VRegA_11n() const;