Fix bug 68629: Transparent artifacts when using imagerotate

We port the respective upstream fix[1], which dropped the special cased
implementations of fixed-point arithmetic rotation in favor of the
generic implementation.

We also port follow-up upstream fixes[2][3].

[1] <libgd/libgd@bd6d2e1>
[2] <libgd/libgd@6d21d30>
[3] <libgd/libgd@9df878a>

Closes GH-17375.

Author: cmb69

NEWS

@@ -32,6 +32,10 @@ PHP                                                                        NEWS
 - Enchant:
   . Added enchant_dict_remove_from_session(). (nielsdos)
 
+-GD:
+  . Fixed bug #68629 (Transparent artifacts when using imagerotate). (pierre,
+    cmb)
+
 - Intl:
   . Bumped ICU requirement to ICU >= 57.1. (cmb)
   . IntlDateFormatter::setTimeZone()/datefmt_set_timezone() throws an exception

ext/gd/libgd/gd.h

@@ -145,7 +145,8 @@ typedef enum {
 	GD_SINC,
 	GD_TRIANGLE,
 	GD_WEIGHTED4,
-	GD_METHOD_COUNT = 21
+	GD_LINEAR,
+	GD_METHOD_COUNT = 22
 } gdInterpolationMethod;
 
 /* define struct with name and func ptr and add it to gdImageStruct gdInterpolationMethod interpolation; */