Fix #78792: zlib.output_compression disabled by Content-Type: image/

Disabling output compression for images has served to fix bug php#16109,
where zlib compressed images apparently have caused issues with
Navigator 4.  This shouldn't be an issue with somewhat contemporary
browsers.  Other than that, this is an arbitrary restriction – why
don't we disable the compression for some other media types as well
(e.g. video/* and audio/*)?  All in all, we should leave that decision
to userland.

Closes phpGH-6198.

NEWS

@@ -18,6 +18,10 @@ PHP                                                                        NEWS
 - SPL:
   . SplFixedArray is now IteratorAggregate rather than Iterator. (alexdowad)
 
+- Zlib:
+  . Fixed bug #78792 (zlib.output_compression disabled by Content-Type: image/).
+    (cmb)
+
 17 Sep 2020, PHP 8.0.0beta4
 
 - Core:

UPGRADING

@@ -662,6 +662,8 @@ PHP 8.0 UPGRADE NOTES
   . deflate_init() will now return a DeflateContext object rather than a
     resource. Return value checks using is_resource() should be replaced with
     checks for `false`.
+  . zlib.output_compression is no longer automatically disabled for
+    Content-Type: image/*.
 
 ========================================
 2. New Features

main/SAPI.c

@@ -762,13 +762,6 @@ SAPI_API int sapi_header_op(sapi_header_op_enum op, void *arg)
 					len--;
 				}
 
-				/* Disable possible output compression for images */
-				if (!strncmp(ptr, "image/", sizeof("image/")-1)) {
-					zend_string *key = zend_string_init("zlib.output_compression", sizeof("zlib.output_compression")-1, 0);
-					zend_alter_ini_entry_chars(key, "0", sizeof("0") - 1, PHP_INI_USER, PHP_INI_STAGE_RUNTIME);
-					zend_string_release_ex(key, 0);
-				}
-
 				mimetype = estrdup(ptr);
 				newlen = sapi_apply_default_charset(&mimetype, len);
 				if (!SG(sapi_headers).mimetype){