Encoding: use uint16_t when interacting with the window object

The ESN, SSN and uncompress bitmap len are uint16_t. The Window is using uint16_t in
function arguments and return values. Don't do so many integer conversions.

Change-Id: If62fa09d7bfa8e91ce707824f7019edb1b83da9e
diff --git a/src/encoding.cpp b/src/encoding.cpp
index 0afd55d..90b4a8c 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -837,14 +837,14 @@
 	uint8_t len;
 	bool bow = true;
 	bool eow = true;
-	int ssn = window->mod_sns(window->v_q() + 1);
+	uint16_t ssn = window->mod_sns(window->v_q() + 1);
 	unsigned int num_blocks = window->mod_sns(window->v_r() - window->v_q());
-	int esn_crbb = window->mod_sns(ssn - 1);
+	uint16_t esn_crbb = window->mod_sns(ssn - 1);
 	static  uint8_t rbb[RLC_EGPRS_MAX_WS] = {'\0'};
 	uint8_t iter = 0;
 	int is_compressed = 0;
 	bool try_compression = false;
-	uint8_t ucmp_bmplen;
+	uint16_t ucmp_bmplen;
 	uint8_t crbb_bitmap[23] = {'\0'};
 	bitvec ucmp_vec;
 	bitvec crbb_vec;