Use the proper lower bound when doing saturation arithmetic.

16 bit signed integers have a range of [-32768, 32768).  The existing code
was using the interval (-32768, 32768) instead.  This patch fixes that.

Review: https://reviewboard.asterisk.org/r/2479/
........

Merged revisions 386929 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@386930 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/utils.h

@@ -324,8 +324,8 @@ static force_inline void ast_slinear_saturated_add(short *input, short *value)
 	res = (int) *input + *value;
 	if (res > 32767)
 		*input = 32767;
-	else if (res < -32767)
-		*input = -32767;
+	else if (res < -32768)
+		*input = -32768;
 	else
 		*input = (short) res;
 }
@@ -337,8 +337,8 @@ static force_inline void ast_slinear_saturated_subtract(short *input, short *val
 	res = (int) *input - *value;
 	if (res > 32767)
 		*input = 32767;
-	else if (res < -32767)
-		*input = -32767;
+	else if (res < -32768)
+		*input = -32768;
 	else
 		*input = (short) res;
 }
@@ -350,8 +350,8 @@ static force_inline void ast_slinear_saturated_multiply(short *input, short *val
 	res = (int) *input * *value;
 	if (res > 32767)
 		*input = 32767;
-	else if (res < -32767)
-		*input = -32767;
+	else if (res < -32768)
+		*input = -32768;
 	else
 		*input = (short) res;
 }