py: Clean up includes.

Remove unnecessary includes. Add includes that improve portability.

py/asmthumb.c

-#include <stdint.h>
 #include <stdio.h>
 #include <assert.h>
 #include <string.h>

py/binary.c

-#include <stdlib.h>
 #include <stdint.h>
 #include <assert.h>
 

py/builtin.c

-#include <stdint.h>
-#include <stdlib.h>
 #include <stdio.h>
-#include <stdarg.h>
-#include <string.h>
 #include <assert.h>
 
 #include "nlr.h"

py/builtinevex.c

 #include <stdint.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdarg.h>
-#include <string.h>
-#include <assert.h>
 
 #include "nlr.h"
 #include "misc.h"

py/builtinimport.c

 #include <stdint.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include <stdarg.h>
 #include <string.h>
 #include <assert.h>
 

py/builtinmath.c

-#include <stdint.h>
 #include <math.h>
 
 #include "misc.h"

py/builtinmp.c

-#include <stdint.h>
 
 #include "misc.h"
 #include "mpconfig.h"

py/compile.c

-#include <unistd.h>
-#include <stdlib.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>

py/emitbc.c

-#include <unistd.h>
-#include <stdlib.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>

py/emitcommon.c

 #include <unistd.h>
-#include <stdio.h>
 #include <stdint.h>
-#include <string.h>
 #include <assert.h>
 
 #include "misc.h"

py/emitcpy.c

-#include <unistd.h>
-#include <stdlib.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>

py/emitinlinethumb.c

-#include <unistd.h>
-#include <stdlib.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>

py/emitnative.c

@@ -16,8 +16,7 @@
 
 // for x in l[0:8]: can be compiled into a native loop if l has pointer type
 
-#include <unistd.h>
-#include <stdlib.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>

py/emitpass1.c

-#include <unistd.h>
 #include <stdlib.h>
 #include <stdint.h>
-#include <stdio.h>
-#include <string.h>
 #include <assert.h>
 
 #include "misc.h"

py/formatfloat.c

@@ -13,7 +13,6 @@
 
 ***********************************************************************/
 
-#include <stdint.h>
 #include <stdlib.h>
 
 #include "mpconfig.h"

py/gc.c

 #include <stdio.h>
 #include <stdlib.h>
-#include <stdint.h>
 #include <string.h>
 
 #include "mpconfig.h"

py/lexer.c

 /* lexer.c -- simple tokeniser for Python implementation
  */
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
-#include <string.h>
 #include <assert.h>
 
 #include "misc.h"

py/lexerstr.c

-#include <stdint.h>
-#include <stdio.h>
 
 #include "misc.h"
 #include "mpconfig.h"

py/lexerunix.c

-#include <stdint.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -11,6 +10,9 @@
 
 #if MICROPY_ENABLE_LEXER_UNIX
 
+#include <sys/stat.h>
+#include <sys/types.h>
+
 mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
     int fd = open(filename, O_RDONLY);
     if (fd < 0) {

py/malloc.c

+#include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>