pass string by reference instead of by value

Should not make that big difference, but still. Should not be BIC in practice
because it's inline.

Change-Id: I53ec7dec46356fb63b0f6f73579cff1ca8495fbf

sal/inc/rtl/strbuf.hxx

@@ -143,7 +143,7 @@ public:
 
         @param   value   the initial string value.
      */
-    OStringBuffer(OString value)
+    OStringBuffer(const OString& value)
         : pData(NULL)
         , nCapacity( value.getLength() + 16 )
     {

sal/inc/rtl/ustrbuf.hxx

@@ -138,7 +138,7 @@ public:
 
         @param   value   the initial contents of the buffer.
      */
-    OUStringBuffer(OUString value)
+    OUStringBuffer(const OUString& value)
         : pData(NULL)
         , nCapacity( value.getLength() + 16 )
     {