Moving pymalloc along.

+ Redirect PyMem_{Del, DEL} to the object allocator's free() when
  pymalloc is enabled.  Needed so old extensions can continue to
  mix PyObject_New with PyMem_DEL.

+ This implies that pgen needs to be able to see the PyObject_XYZ
  declarations too.  pgenheaders.h now includes Python.h.  An
  implication is that I expect obmalloc.o needs to get linked into
  pgen on non-Windows boxes.

+ When PYMALLOC_DEBUG is defined, *all* Py memory API functions
  now funnel through the debug allocator wrapper around pymalloc.
  This is the default in a debug build.

+ That caused compile.c to fail:  it indirectly mixed PyMem_Malloc
  with raw platform free() in one place.  This is verbotten.

Python/compile.c

@@ -1954,7 +1954,7 @@ com_factor(struct compiling *c, node *n)
 			return;
 		}
 		if (childtype == MINUS) {
-			char *s = malloc(strlen(STR(pnum)) + 2);
+			char *s = PyMem_Malloc(strlen(STR(pnum)) + 2);
 			if (s == NULL) {
 				com_error(c, PyExc_MemoryError, "");
 				com_addbyte(c, 255);
@@ -1962,7 +1962,7 @@ com_factor(struct compiling *c, node *n)
 			}
 			s[0] = '-';
 			strcpy(s + 1, STR(pnum));
-			free(STR(pnum));
+			PyMem_Free(STR(pnum));
 			STR(pnum) = s;
 		}
 		com_atom(c, patom);