Fix several MSVC compiler warnings

Change-Id: I88d2211ed3bac1813633ee9100e18f7a6d7e74f0
diff --git a/av1/common/convolve.c b/av1/common/convolve.c
index 28416c7..f20aaf9 100644
--- a/av1/common/convolve.c
+++ b/av1/common/convolve.c
@@ -28,8 +28,8 @@
 
 void av1_convolve_horiz_rs_c(const uint8_t *src, int src_stride, uint8_t *dst,
                              int dst_stride, int w, int h,
-                             const int16_t *x_filters, const int x0_qn,
-                             const int x_step_qn) {
+                             const int16_t *x_filters, int x0_qn,
+                             int x_step_qn) {
   src -= UPSCALE_NORMATIVE_TAPS / 2 - 1;
   for (int y = 0; y < h; ++y) {
     int x_qn = x0_qn;
diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index d761882..c6539b5 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -5983,7 +5983,7 @@
     // move the rest of data to new location
     memmove(buff_ptr + length_of_obu_size + obu_header_size,
             buff_ptr + obu_bytes_read, remaining_size - obu_bytes_read);
-    obu_bytes_read += obu_payload_size;
+    obu_bytes_read += (size_t)obu_payload_size;
 
     // write the new obu size
     const uint64_t obu_size = obu_header_size + obu_payload_size;
@@ -5999,7 +5999,7 @@
     total_bytes_read += obu_bytes_read;
     remaining_size -= obu_bytes_read;
     buff_ptr += length_of_obu_size + obu_size;
-    output_size += length_of_obu_size + obu_size;
+    output_size += length_of_obu_size + (size_t)obu_size;
   }
 
   *frame_size = output_size;
diff --git a/obudec.c b/obudec.c
index 4b5bda3..0974178 100644
--- a/obudec.c
+++ b/obudec.c
@@ -133,7 +133,7 @@
     return -1;
   }
 
-  *bytes_read += payload_length;
+  *bytes_read += (size_t)payload_length;
   return 0;
 }