Add encoders for state sensor/effecter PDRs and sensor event data

Change-Id: I736d1b7b1c124faf8fbf86bb3b760cc9b48c1e2b
Signed-off-by: Zach Clark <zach@ibm.com>
diff --git a/libpldm/base.h b/libpldm/base.h
index dd63f1c..5109c34 100644
--- a/libpldm/base.h
+++ b/libpldm/base.h
@@ -110,6 +110,10 @@
 	uint8_t command; //!< PLDM command code
 } __attribute__((packed));
 
+// Macros for byte-swapping variables in-place
+#define HTOLE32(X) (X = htole32(X))
+#define HTOLE16(X) (X = htole16(X))
+
 /** @struct pldm_msg
  *
  * Structure representing PLDM message