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

Change-Id: Ieef535e34f5acd9139c3ee1e9e6c650fc5fe92e4
Reviewed-on: https://gerrit.libreoffice.org/19842Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

tools/source/generic/config.cxx

@@ -843,14 +843,7 @@ OString Config::ReadKey(const OString& rKey, const OString& rDefault) const
 void Config::WriteKey(const OString& rKey, const OString& rStr)
 {
 #ifdef DBG_UTIL
-    OStringBuffer aTraceStr("Config::WriteKey( ");
-    aTraceStr.append(rKey);
-    aTraceStr.append(", ");
-    aTraceStr.append(rStr);
-    aTraceStr.append(" ) to ");
-    aTraceStr.append(GetGroup());
-    aTraceStr.append(" in ");
-    aTraceStr.append(OUStringToOString(maFileName, RTL_TEXTENCODING_UTF8));
+    OString aTraceStr("Config::WriteKey( " + rKey + ", " + rStr + " ) to " + GetGroup() + " in " + OUStringToOString(maFileName, RTL_TEXTENCODING_UTF8));
     OSL_TRACE("%s", aTraceStr.getStr());
 #endif