docs: Mark internal code as private

* ImportVisitor is relatively new, but was forgotten to be marked as
  private. As such, it became listed on doc.wikimedia.org, even though
  it is not a public or stable API for external usage
  https://doc.wikimedia.org/mediawiki-libs-less.php/

* Idem for several Less_Parser utility functions.

* Fix Doxygen warning about missing param doc for saturate().

* Fix Doxygen warning about invalid param doc for SetImportDirs.

* Remove noise from `@param-` comments on doc.wikimedia.org by
  setting this to noop. We do the same in MediaWiki for example
  https://gerrit.wikimedia.org/g/mediawiki/core/+/2e9414bd80/maintenance/Doxyfile#64

* Hide two internal functions from the output. Note that `@private`
  only works on classes and other entities not explicitly marked
  public. To hide a "public" static function, we use `@internal`
  instead.
  https://www.doxygen.nl/manual/commands.html#cmdprivate

Change-Id: I3b51240577a6aec48045c15c2e7d32d491be655e

Doxyfile

@@ -12,6 +12,7 @@ INPUT                  = README.md API.md SECURITY.md CHANGES.md lib/
 FILE_PATTERNS          = *.php
 RECURSIVE              = YES
 USE_MDFILE_AS_MAINPAGE = README.md
+ALIASES                = "phan=\noop"
 HTML_COLORSTYLE        = LIGHT
 HTML_DYNAMIC_SECTIONS  = YES
 GENERATE_TREEVIEW      = YES

lib/Less/Functions.php

@@ -273,6 +273,7 @@ public function saturate( $color = null, $amount = null, $method = null ) {
 	/**
 	 * @param Less_Tree_Color|null $color
 	 * @param Less_Tree_Dimension|null $amount
+	 * @param Less_Tree_Quoted|Less_Tree_Color|Less_Tree_Keyword|null $method
 	 */
 	public function desaturate( $color = null, $amount = null, $method = null ) {
 		if ( !$color instanceof Less_Tree_Color ) {

lib/Less/ImportVisitor.php

@@ -1,5 +1,7 @@
 <?php
-
+/**
+ * @private
+ */
 class Less_ImportVisitor extends Less_Visitor {
 
 	public $env;

lib/Less/Parser.php

@@ -596,11 +596,11 @@ public function SetCacheDir( $dir ) {
 	 *         }
 	 *     }
 	 *
-	 *
-	 * @param array<string|callable> $dirs The key should be a server directory from which LESS
+	 * @param array $dirs The key should be a server directory from which LESS
 	 * files may be imported. The value is an optional public URL or URL base path that corresponds to
 	 * the same directory (use empty string otherwise). The value may also be a closure, in
 	 * which case the key is ignored.
+	 * @phan-param array<string,string|callable> $dirs
 	 */
 	public function SetImportDirs( $dirs ) {
 		self::$options['import_dirs'] = [];
@@ -3217,6 +3217,7 @@ public static function serializeVars( $vars ) {
 	/**
 	 * Some versions of PHP have trouble with method_exists($a,$b) if $a is not an object
 	 *
+	 * @internal For internal use only
 	 * @param mixed $a
 	 * @param string $b
 	 */
@@ -3227,6 +3228,8 @@ public static function is_method( $a, $b ) {
 	/**
 	 * Round numbers similarly to javascript
 	 * eg: 1.499999 to 1 instead of 2
+	 *
+	 * @internal For internal use only
 	 */
 	public static function round( $input, $precision = 0 ) {
 		$precision = pow( 10, $precision );