Reland "Upconvert various types to int.", neteq portion.

This reverts portions of commit cb180976dd0e9672cde4523d87b5f4857478b5e9, which
reverted commit 83ad33a8aed1fb00e422b6abd33c3e8942821c24.  Specifically, the
files in webrtc/modules/audio_coding/neteq/ are relanded.

The original commit message is below:

Upconvert various types to int.

Per comments from HL/kwiberg on https://webrtc-codereview.appspot.com/42569004 , when there is existing usage of mixed types (int16_t, int, etc.), we'd prefer to standardize on larger types like int and phase out use of int16_t.

Specifically, "Using int16 just because we're sure all reasonable values will fit in 16 bits isn't usually meaningful in C."

This converts some existing uses of int16_t (and, in a few cases, other types such as uint16_t) to int (or, in a few places, int32_t).  Other locations will be converted to size_t in a separate change.

BUG=none
TBR=kwiberg

Review URL: https://codereview.webrtc.org/1181073002

Cr-Commit-Position: refs/heads/master@{#9427}
diff --git a/webrtc/modules/audio_coding/neteq/merge.cc b/webrtc/modules/audio_coding/neteq/merge.cc
index 8e686ba..2c515c1 100644
--- a/webrtc/modules/audio_coding/neteq/merge.cc
+++ b/webrtc/modules/audio_coding/neteq/merge.cc
@@ -314,7 +314,7 @@
   const int max_corr_length = kMaxCorrelationLength;
   int stop_position_downsamp =
       std::min(max_corr_length, expand_->max_lag() / (fs_mult_ * 2) + 1);
-  int16_t correlation_shift = 0;
+  int correlation_shift = 0;
   if (expanded_max * input_max > 26843546) {
     correlation_shift = 3;
   }
@@ -333,7 +333,7 @@
   int16_t* correlation_ptr = &correlation16[pad_length];
   int32_t max_correlation = WebRtcSpl_MaxAbsValueW32(correlation,
                                                      stop_position_downsamp);
-  int16_t norm_shift = std::max(0, 17 - WebRtcSpl_NormW32(max_correlation));
+  int norm_shift = std::max(0, 17 - WebRtcSpl_NormW32(max_correlation));
   WebRtcSpl_VectorBitShiftW32ToW16(correlation_ptr, stop_position_downsamp,
                                    correlation, norm_shift);