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/ilbc/refiner.c

@@ -75,7 +75,7 @@ void WebRtcIlbcfix_Refiner(
 
   /* Calculate the rescaling factor for the correlation in order to
      put the correlation in a int16_t vector instead */
-  maxtemp=WebRtcSpl_MaxAbsValueW32(corrVecTemp, (int16_t)corrdim);
+  maxtemp=WebRtcSpl_MaxAbsValueW32(corrVecTemp, corrdim);
 
   scalefact=WebRtcSpl_GetSizeInBits(maxtemp)-15;
 
@@ -97,7 +97,7 @@ void WebRtcIlbcfix_Refiner(
   WebRtcIlbcfix_EnhUpsample(corrVecUps,corrVec);
 
   /* Find maximum */
-  tloc=WebRtcSpl_MaxIndexW32(corrVecUps, (int16_t) (ENH_UPS0*corrdim));
+  tloc=WebRtcSpl_MaxIndexW32(corrVecUps, ENH_UPS0 * corrdim);
 
   /* make vector can be upsampled without ever running outside
      bounds */