Massive overhaul of Mustache.php's whitespace handling.

Move regex preparation into methods, use named subpatterns so the regex makes more sense. Fix the logic around eating newlines adjacent to tags. Update tests to reflect the changes.

test/MustachePragmaImplicitIteratorTest.php

@@ -11,7 +11,11 @@ class MustachePragmaImplicitIteratorTest extends PHPUnit_Framework_TestCase {
 		$m = $this->getMock('Mustache', array('_renderPragma'), array('{{%IMPLICIT-ITERATOR}}'));
 		$m->expects($this->exactly(1))
 			->method('_renderPragma')
-			->with(array('{{%IMPLICIT-ITERATOR}}', 'IMPLICIT-ITERATOR', null));
+			->with(array(
+				0 => '{{%IMPLICIT-ITERATOR}}',
+				1 => 'IMPLICIT-ITERATOR', 'pragma_name' => 'IMPLICIT-ITERATOR',
+				2 => null, 'options_string' => null
+			));
 		$m->render();
 	}