py, extmod: Remove include of unnecessary system headers.

extmod/moduheapq.c

@@ -24,8 +24,6 @@
  * THE SOFTWARE.
  */
 
-#include <unistd.h>
-
 #include "py/nlr.h"
 #include "py/objlist.h"
 #include "py/runtime0.h"

extmod/modujson.c

@@ -25,8 +25,6 @@
  */
 
 #include <stdio.h>
-#include <unistd.h>
-#include <string.h>
 
 #include "py/nlr.h"
 #include "py/objlist.h"

extmod/moduzlib.c

@@ -25,11 +25,6 @@
  */
 
 #include <stdio.h>
-#include <unistd.h>
-#include <string.h>
-#include <time.h>
-#include <sys/time.h>
-#include <math.h>
 
 #include "py/nlr.h"
 #include "py/runtime.h"

py/compile.c

@@ -29,7 +29,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <assert.h>
-#include <math.h>
 
 #include "py/scope.h"
 #include "py/emit.h"

py/objfloat.c

@@ -28,7 +28,6 @@
 #include <stdio.h>
 #include <string.h>
 #include <assert.h>
-#include <math.h>
 
 #include "py/nlr.h"
 #include "py/parsenum.h"
@@ -37,6 +36,8 @@
 
 #if MICROPY_PY_BUILTINS_FLOAT
 
+#include <math.h>
+
 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
 #include "py/formatfloat.h"
 #endif