Issue #5835, deprecate PyOS_ascii_formatd.

If anyone wants to clean up the documentation, feel free. It's my first documentation foray, and it's not that great.

Will port to py3k with a different strategy.
diff --git a/Modules/cPickle.c b/Modules/cPickle.c
index fb13ba1..6c7ed99 100644
--- a/Modules/cPickle.c
+++ b/Modules/cPickle.c
@@ -1166,7 +1166,8 @@
 	else {
 		char c_str[250];
 		c_str[0] = FLOAT;
-		PyOS_ascii_formatd(c_str + 1, sizeof(c_str) - 2, "%.17g", x);
+		_PyOS_double_to_string(c_str + 1, sizeof(c_str) - 2, x, 'g',
+                                       17, 0, NULL);
 		/* Extend the formatted string with a newline character */
 		strcat(c_str, "\n");