Add cpp specific include snippet

The standard inclusion template has been changed from "stdio.h" to
iostream. In case of C++, the user most likely will work with STL
containers/headers which by default don't require the ".h" extension.

snippets/cpp.snippets

@@ -1,5 +1,11 @@
 extends c
 
+##
+## Preprocessor
+# #include <...>
+snippet inc
+	#include <${1:iostream}>
+##
 ## STL Collections
 # std::array
 snippet array