Improve link styling in PHPInfo (php#15077)

* Improve link styling in PHPInfo

The previous styling with the fixed background color didn't work well in dark
mode. Remove the background and make links inherit the regular text color. To
make them visually detectable the underlining behavior is reversed. The
underline is now shown when not hovering and hidden when hovering.

* Preserve the headline linking behavior

ext/standard/css.c

@@ -21,8 +21,8 @@ PHPAPI ZEND_COLD void php_info_print_css(void) /* {{{ */
 {
 	PUTS("body {background-color: #fff; color: #222; font-family: sans-serif;}\n");
 	PUTS("pre {margin: 0; font-family: monospace;}\n");
-	PUTS("a:link {color: #009; text-decoration: none; background-color: #fff;}\n");
-	PUTS("a:hover {text-decoration: underline;}\n");
+	PUTS("a {color: inherit;}\n");
+	PUTS("a:hover {text-decoration: none;}\n");
 	PUTS("table {border-collapse: collapse; border: 0; width: 934px; box-shadow: 1px 2px 3px rgba(0, 0, 0, 0.2);}\n");
 	PUTS(".center {text-align: center;}\n");
 	PUTS(".center table {margin: 1em auto; text-align: left;}\n");
@@ -31,7 +31,8 @@ PHPAPI ZEND_COLD void php_info_print_css(void) /* {{{ */
 	PUTS("th {position: sticky; top: 0; background: inherit;}\n");
 	PUTS("h1 {font-size: 150%;}\n");
 	PUTS("h2 {font-size: 125%;}\n");
-	PUTS("h2 a:link, h2 a:visited{color: inherit; background: inherit;}\n");
+	PUTS("h2 > a {text-decoration: none;}\n");
+	PUTS("h2 > a:hover {text-decoration: underline;}\n");
 	PUTS(".p {text-align: left;}\n");
 	PUTS(".e {background-color: #ccf; width: 300px; font-weight: bold;}\n");
 	PUTS(".h {background-color: #99c; font-weight: bold;}\n");