[MERGE #4374 @sigatrev] Sym bitfield member type

Merge pull request #4374 from sigatrev:mem

This was inceasing the size of StackSym.

lib/Backend/Sym.h

@@ -231,7 +231,7 @@ public:
     uint8           m_isArgCaptured: 1;       // True if there is a ByteCodeArgOutCapture for this symbol
     uint8           m_nonEscapingArgObjAlias : 1;
     uint8           m_isCatchObjectSym : 1;   // a catch object sym (used while jitting loop bodies)
-    uint            m_isClosureSym : 1;
+    uint8           m_isClosureSym : 1;
     IRType          m_type;
     Js::BuiltinFunction m_builtInIndex;