Match existing type usage better.

This makes a variety of small changes to synchronize bits of code using different types, remove useless code or casts, and add explicit casts in some places previously doing implicit ones.  For example:

* Change a few type declarations to better match how the majority of code uses those objects.
* Eliminate "< 0" check for unsigned values.
* Replace "(float)sin(x)", where |x| is also a float, with "sinf(x)", and similar.
* Add casts to uint32_t in many places timestamps were used and the existing code stored signed values into the unsigned objects.
* Remove downcasts when the results would be passed to a larger type, e.g. calling "foo((int16_t)x)" with an int |x| when foo() takes an int instead of an int16_t.
* Similarly, add casts when passing a larger type to a function taking a smaller one.
* Add casts to int16_t when doing something like "int16_t = int16_t + int16_t" as the "+" operation would implicitly upconvert to int, and similar.
* Use "false" instead of "0" for setting a bool.
* Shift a few temp types when doing a multi-stage calculation involving typecasts, so as to put the most logical/semantically correct type possible into the temps.  For example, when doing "int foo = int + int; size_t bar = (size_t)foo + size_t;", we might change |foo| to a size_t and move the cast if it makes more sense for |foo| to be represented as a size_t.

BUG=none
R=andrew@webrtc.org, asapersson@webrtc.org, henrika@webrtc.org, juberti@webrtc.org, kwiberg@webrtc.org
TBR=andrew, asapersson, henrika

Review URL: https://codereview.webrtc.org/1168753002

Cr-Commit-Position: refs/heads/master@{#9419}

webrtc/modules/audio_coding/codecs/isac/fix/source/bandwidth_estimator.c

@@ -374,7 +374,7 @@ int32_t WebRtcIsacfix_UpdateUplinkBwImpl(BwEstimatorstr *bweStr,
         /* compute inverse receiving rate for last packet, in Q19 */
         numBytesInv = (uint16_t) WebRtcSpl_DivW32W16(
             524288 + ((pksize + HEADER_SIZE) >> 1),
-            pksize + HEADER_SIZE);
+            (int16_t)(pksize + HEADER_SIZE));
 
         /* 8389 is  ~ 1/128000 in Q30 */
         byteSecondsPerBit = (uint32_t)(arrTimeDiff * 8389);

webrtc/modules/audio_coding/codecs/isac/fix/source/decode_plc.c

@@ -447,7 +447,7 @@ int16_t WebRtcIsacfix_DecodePlcImpl(int16_t *signal_out16,
   /* inverse pitch filter */
 
   pitchLags_Q7[0] = pitchLags_Q7[1] = pitchLags_Q7[2] = pitchLags_Q7[3] =
-      ((ISACdec_obj->plcstr_obj).stretchLag<<7);
+      (int16_t)((ISACdec_obj->plcstr_obj).stretchLag<<7);
   pitchGains_Q12[3] = ( (ISACdec_obj->plcstr_obj).lastPitchGain_Q12);
   pitchGains_Q12[2] = (int16_t)(pitchGains_Q12[3] * 1010 >> 10);
   pitchGains_Q12[1] = (int16_t)(pitchGains_Q12[2] * 1010 >> 10);
@@ -749,7 +749,8 @@ int16_t WebRtcIsacfix_DecodePlcImpl(int16_t *signal_out16,
     k = ( k < ((ISACdec_obj->plcstr_obj).stretchLag - 1) )? (k+1):0;
   }
 
-  (ISACdec_obj->plcstr_obj).lastPitchLag_Q7 = (ISACdec_obj->plcstr_obj).stretchLag << 7;
+  (ISACdec_obj->plcstr_obj).lastPitchLag_Q7 =
+      (int16_t)((ISACdec_obj->plcstr_obj).stretchLag << 7);
 
 
   /* --- Inverse Pitch Filter --- */

webrtc/modules/audio_coding/codecs/isac/fix/source/encode.c

@@ -498,7 +498,7 @@ int WebRtcIsacfix_EncodeStoredData(IsacFixEncoderInstance  *ISACenc_obj,
 {
   int ii;
   int status;
-  int16_t BWno = BWnumber;
+  int16_t BWno = (int16_t)BWnumber;
   int stream_length = 0;
 
   int16_t model;

webrtc/modules/audio_coding/codecs/isac/fix/source/isacfix.c

@@ -425,7 +425,8 @@ int16_t WebRtcIsacfix_Encode(ISACFIX_MainStruct *ISAC_main_inst,
     return -1;
   }
 
-  write_be16(ISAC_inst->ISACenc_obj.bitstr_obj.stream, stream_len, encoded);
+  write_be16(ISAC_inst->ISACenc_obj.bitstr_obj.stream, (size_t)stream_len,
+             encoded);
   return stream_len;
 
 }