Use 'frame' instead of 'signal', take out stdlib.h in silk/.

On MacOS, stdlib.h ends up including sys/signal.h, generating
warnings about the local variables called 'signal' shadowing
the global symbol signal(3).

This was originally done in 86476906 but it missed some use
of 'signal' in prototypes in headers where it didn't cause
warnings. Later the prototypes were moved around and the
warnings came back.

This also cleans up some cases in where stdlib.h was used
but shouldn't be required.

silk/MacroCount.h

@@ -477,7 +477,7 @@ static inline opus_int64 silk_abs_int64(opus_int64 a){
 #undef    silk_abs_int32
 static inline opus_int32 silk_abs_int32(opus_int32 a){
     ops_count += 1;
-    return abs(a);
+    return silk_abs(a);
 }
 
 

silk/MacroDebug.h

@@ -893,7 +893,7 @@ static inline opus_int32 silk_abs_int32_(opus_int32 a, char *file, int line){
         silk_assert( 0 );
 #endif
     }
-    return abs(a);
+    return silk_abs(a);
 }
 
 #undef silk_CHECK_FIT8

silk/PLC.c

@@ -45,7 +45,7 @@ static inline void silk_PLC_update(
 static inline void silk_PLC_conceal(
     silk_decoder_state                  *psDec,             /* I/O Decoder state        */
     silk_decoder_control                *psDecCtrl,         /* I/O Decoder control      */
-    opus_int16                          signal[]            /* O LPC residual signal    */
+    opus_int16                          frame[]             /* O LPC residual signal    */
 );
 
 

silk/SigProc_FIX.h

@@ -37,7 +37,6 @@ extern "C"
 
 #define SILK_MAX_ORDER_LPC            16            /* max order of the LPC analysis in schur() and k2a() */
 
-#include <stdlib.h>                                 /* for abs() */
 #include <string.h>                                 /* for memset(), memcpy(), memmove() */
 #include "typedef.h"
 #include "resampler_structs.h"

silk/VAD.c

@@ -29,7 +29,6 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "config.h"
 #endif
 
-#include <stdlib.h>
 #include "main.h"
 
 /* Silk VAD noise level estimation */