audio_coding/codec/ilbc: Removed usage of macro WEBRTC_SPL_MUL_16_16

The macro is in C defined as
#define WEBRTC_SPL_MUL_16_16(a, b) ((int32_t) (((int16_t)(a)) * ((int16_t)(b))))
(For definition on ARMv7 and MIPS, see common_audio/signal_processing/include/spl_inl_armv7.h and common_audio/signal_processing/include/spl_inl_mips.h)

The replacement consists of
- avoiding casts to int16_t if inputs already are int16_t
- adding explicit cast to <type> if result is assigned to <type> (other than int or int32_t)

Some other minor code cleanup also exists.

BUG=3348, 3353
TESTED=locally on Mac and trybots
R=henrik.lundin@webrtc.org, kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/34179004

Cr-Commit-Position: refs/heads/master@{#8358}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8358 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/codecs/ilbc/refiner.c

@@ -101,7 +101,7 @@ void WebRtcIlbcfix_Refiner(
 
   /* make vector can be upsampled without ever running outside
      bounds */
-  *updStartPos = (int16_t)WEBRTC_SPL_MUL_16_16(searchSegStartPos,4) + tloc + 4;
+  *updStartPos = (int16_t)(searchSegStartPos * 4) + tloc + 4;
 
   tloc2 = (tloc + 3) >> 2;
 
@@ -127,7 +127,7 @@ void WebRtcIlbcfix_Refiner(
     }
   }
   /* Calculate which of the 4 fractions to use */
-  fraction=(int16_t)WEBRTC_SPL_MUL_16_16(tloc2,ENH_UPS0)-tloc;
+  fraction = (int16_t)(tloc2 * ENH_UPS0) - tloc;
 
   /* compute the segment (this is actually a convolution) */