Fix for the Image_lib clear() function so that it resets all variables to their default values.

This should fix issues #157 and #174.
https://github.com/EllisLab/CodeIgniter/issues/157
https://github.com/EllisLab/CodeIgniter/issues/174
diff --git a/system/libraries/Image_lib.php b/system/libraries/Image_lib.php
index 8902f52..6855e44 100644
--- a/system/libraries/Image_lib.php
+++ b/system/libraries/Image_lib.php
@@ -104,15 +104,37 @@
 	 */
 	function clear()
 	{
-		$props = array('source_folder', 'dest_folder', 'source_image', 'full_src_path', 'full_dst_path', 'new_image', 'image_type', 'size_str', 'quality', 'orig_width', 'orig_height', 'rotation_angle', 'x_axis', 'y_axis', 'create_fnc', 'copy_fnc', 'wm_overlay_path', 'wm_use_truetype', 'dynamic_output', 'wm_font_size', 'wm_text', 'wm_vrt_alignment', 'wm_hor_alignment', 'wm_padding', 'wm_hor_offset', 'wm_vrt_offset', 'wm_font_color', 'wm_use_drop_shadow', 'wm_shadow_color', 'wm_shadow_distance', 'wm_opacity');
+		$props = array('library_path', 'source_image', 'new_image', 'width', 'height', 'rotation_angle', 'x_axis', 'y_axis', 'wm_text', 'wm_overlay_path', 'wm_font_path', 'wm_shadow_color', 'source_folder', 'dest_folder', 'mime_type', 'orig_width', 'orig_height', 'image_type', 'size_str', 'full_src_path', 'full_dst_path');
 
 		foreach ($props as $val)
 		{
 			$this->$val = '';
 		}
 
-		// special consideration for master_dim
-		$this->master_dim = 'auto';
+		$this->image_library 		= 'gd2';
+		$this->dynamic_output 		= FALSE;
+		$this->quality 				= '90';
+		$this->create_thumb 		= FALSE;
+		$this->thumb_marker 		= '_thumb';
+		$this->maintain_ratio 		= TRUE;
+		$this->master_dim 			= 'auto';
+		$this->wm_type 				= 'text';
+		$this->wm_x_transp 			= 4;
+		$this->wm_y_transp 			= 4;
+		$this->wm_font_size 		= 17;
+		$this->wm_vrt_alignment 	= 'B';
+		$this->wm_hor_alignment 	= 'C';
+		$this->wm_padding 			= 0;
+		$this->wm_hor_offset 		= 0;
+		$this->wm_vrt_offset 		= 0;
+		$this->wm_font_color		= '#ffffff';
+		$this->wm_shadow_distance 	= 2;
+		$this->wm_opacity 			= 50;
+		$this->create_fnc 			= 'imagecreatetruecolor';
+		$this->copy_fnc 			= 'imagecopyresampled';
+		$this->error_msg 			= array();
+		$this->wm_use_drop_shadow 	= FALSE;
+		$this->wm_use_truetype 		= FALSE;
 	}
 
 	// --------------------------------------------------------------------