Issue #16330: Use surrogate-related macros

Patch written by Serhiy Storchaka.
diff --git a/Python/codecs.c b/Python/codecs.c
index 5470500..5cfb1c9 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -761,7 +761,7 @@
         for (i = start; i < end; i++) {
             /* object is guaranteed to be "ready" */
             Py_UCS4 ch = PyUnicode_READ_CHAR(object, i);
-            if (ch < 0xd800 || ch > 0xdfff) {
+            if (!Py_UNICODE_IS_SURROGATE(ch)) {
                 /* Not a surrogate, fail with original exception */
                 PyErr_SetObject(PyExceptionInstance_Class(exc), exc);
                 Py_DECREF(res);
@@ -797,7 +797,7 @@
              (p[2] & 0xc0) == 0x80)) {
             /* it's a three-byte code */
             ch = ((p[0] & 0x0f) << 12) + ((p[1] & 0x3f) << 6) + (p[2] & 0x3f);
-            if (ch < 0xd800 || ch > 0xdfff)
+            if (!Py_UNICODE_IS_SURROGATE(ch))
                 /* it's not a surrogate - fail */
                 ch = 0;
         }
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 501cb8c..526751d 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -85,7 +85,7 @@
             /* Only use the result if it contains no
                surrogate characters. */
             for (tmp = res; *tmp != 0 &&
-                         (*tmp < 0xd800 || *tmp > 0xdfff); tmp++)
+                         !Py_UNICODE_IS_SURROGATE(*tmp); tmp++)
                 ;
             if (*tmp == 0) {
                 if (size != NULL)
@@ -131,7 +131,7 @@
             memset(&mbs, 0, sizeof mbs);
             continue;
         }
-        if (*out >= 0xd800 && *out <= 0xdfff) {
+        if (Py_UNICODE_IS_SURROGATE(*out)) {
             /* Surrogate character.  Escape the original
                byte sequence with surrogateescape. */
             argsize -= converted;