Add sizeof, decltype, and declval snippets

UltiSnips/c.snippets

@@ -11,6 +11,10 @@ def complete(t, opts):
 	return '(' + '|'.join(opts) + ')'
 endglobal
 
+snippet sizeof "sizeof" i
+sizeof($1)$0
+endsnippet
+
 snippet i8 "int8_t" i
 int8_t
 endsnippet

UltiSnips/cpp.snippets

@@ -65,6 +65,14 @@ snippet static_assert "Static assert"
 static_assert($1, "$2");
 endsnippet
 
+snippet decltype "decltype" i
+decltype($1)$0
+endsnippet
+
+snippet declval "declval" i
+declval<$1>()$0
+endsnippet
+
 snippet noisy "A noise class"
 class noisy_t {
  public: