tdf#57950 Replace chained O(U)StringBuffer::append() with operator+

Change-Id: Id9bc24079d3840277d6fc10197a4f27373f4bd25
Reviewed-on: https://gerrit.libreoffice.org/19225Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>

tools/source/generic/config.cxx

@@ -815,12 +815,7 @@ OString Config::ReadKey(const OString& rKey) const
 OString Config::ReadKey(const OString& rKey, const OString& rDefault) const
 {
 #ifdef DBG_UTIL
-    OStringBuffer aTraceStr("Config::ReadKey( ");
-    aTraceStr.append(rKey);
-    aTraceStr.append(" ) from ");
-    aTraceStr.append(GetGroup());
-    aTraceStr.append(" in ");
-    aTraceStr.append(OUStringToOString(maFileName, RTL_TEXTENCODING_UTF8));
+    OString aTraceStr("Config::ReadKey( " + rKey + " ) from " + GetGroup() + " in " + OUStringToOString(maFileName, RTL_TEXTENCODING_UTF8));
     OSL_TRACE("%s", aTraceStr.getStr());
 #endif