Change version number to 1.2.18

Changed for library version
diff --git a/doxygen/input/doc_mainpage.h b/doxygen/input/doc_mainpage.h
index dd359bb..dcb983f 100644
--- a/doxygen/input/doc_mainpage.h
+++ b/doxygen/input/doc_mainpage.h
@@ -4,7 +4,7 @@
  */
 
 /**
- * @mainpage PolarSSL v1.2.17 source code documentation
+ * @mainpage PolarSSL v1.2.18 source code documentation
  * 
  * This documentation describes the internal structure of PolarSSL.  It was
  * automatically generated from specially formatted comment blocks in