added constants.php file and implemented constants for file system modes
diff --git a/system/libraries/Image_lib.php b/system/libraries/Image_lib.php
index 3957420..85435f6 100644
--- a/system/libraries/Image_lib.php
+++ b/system/libraries/Image_lib.php
@@ -484,7 +484,7 @@
 					return FALSE;

 				}

 			

-				@chmod($this->full_dst_path, 0777);

+				@chmod($this->full_dst_path, DIR_WRITE_MODE);

 				return TRUE;

 			}

 			

@@ -539,7 +539,7 @@
 		imagedestroy($src_img);

 		

 		// Set the file to 777

-		@chmod($this->full_dst_path, 0777);

+		@chmod($this->full_dst_path, DIR_WRITE_MODE);

 		

 		return TRUE;

 	}

@@ -609,7 +609,7 @@
 		}

 		

 		// Set the file to 777

-		@chmod($this->full_dst_path, 0777);

+		@chmod($this->full_dst_path, DIR_WRITE_MODE);

 		

 		return TRUE;

 	}

@@ -695,7 +695,7 @@
 		// we have to rename the temp file.

 		copy ($this->dest_folder.'netpbm.tmp', $this->full_dst_path);

 		unlink ($this->dest_folder.'netpbm.tmp');

-		@chmod($dst_image, 0777);

+		@chmod($dst_image, DIR_WRITE_MODE);

 		

 		return TRUE;

 	}

@@ -754,7 +754,7 @@
 		

 		// Set the file to 777

 		

-		@chmod($this->full_dst_path, 0777);

+		@chmod($this->full_dst_path, DIR_WRITE_MODE);

 		

 		return true;

 	}

@@ -838,7 +838,7 @@
 		imagedestroy($src_img);

 		

 		// Set the file to 777

-		@chmod($this->full_dst_path, 0777);

+		@chmod($this->full_dst_path, DIR_WRITE_MODE);

 		

 		return TRUE;

 	}

diff --git a/system/libraries/Log.php b/system/libraries/Log.php
index f9ca85a..1aa8bd0 100644
--- a/system/libraries/Log.php
+++ b/system/libraries/Log.php
@@ -109,7 +109,7 @@
 		flock($fp, LOCK_UN);

 		fclose($fp);

 	

-		@chmod($filepath, 0666); 		

+		@chmod($filepath, FILE_WRITE_MODE); 		

 		return TRUE;

 	}

 

diff --git a/system/libraries/Output.php b/system/libraries/Output.php
index a4d8d34..07990eb 100644
--- a/system/libraries/Output.php
+++ b/system/libraries/Output.php
@@ -308,7 +308,7 @@
 		fwrite($fp, $expire.'TS--->'.$output);

 		flock($fp, LOCK_UN);

 		fclose($fp);

-		@chmod($cache_path, 0777);

+		@chmod($cache_path, DIR_WRITE_MODE);

 

 		log_message('debug', "Cache file written: ".$cache_path);

 	}