prefer OUStringBuffer to concatenating OUString in a loop

And improve OUString readability and efficiency.
See: https://goo.gl/jsVAwy:

Change-Id: I8d847b1ca3cde7cb8733d6f8a649612745cf6aae
Reviewed-on: https://gerrit.libreoffice.org/26511
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
diff --git a/basic/source/basmgr/basmgr.cxx b/basic/source/basmgr/basmgr.cxx
index 9b8cf68..918d61d 100644
--- a/basic/source/basmgr/basmgr.cxx
+++ b/basic/source/basmgr/basmgr.cxx
@@ -1626,29 +1626,32 @@ ErrCode BasicManager::ExecuteMacro( OUString const& i_fullyQualifiedName, OUStri
        sArgs.remove( 0, 1 );
        sArgs.remove( sArgs.getLength() - 1, 1 );

        sQuotedArgs = "(";
        OUStringBuffer aBuff;
        OUString sArgs2 = sArgs.makeStringAndClear();
        sal_Int32 nCount = comphelper::string::getTokenCount(sArgs2, ',');

        aBuff.append("(");
        for (sal_Int32 n = 0; n < nCount; ++n)
        {
            sQuotedArgs += "\"";
            sQuotedArgs += sArgs2.getToken(n, ',');
            sQuotedArgs += "\"";
            aBuff.append( "\"" );
            aBuff.append( sArgs2.getToken(n, ',') );
            aBuff.append( "\"" );

            if ( n < nCount - 1 )
            {
                sQuotedArgs += ",";
                aBuff.append( "," );
            }
        }
        aBuff.append( ")" );

        sQuotedArgs += ")";
        sQuotedArgs = aBuff.makeStringAndClear();
    }

    // add quoted arguments and do the call
    OUString sCall;
    sCall += "[";
    sCall += pMethod->GetName();
    sCall += sQuotedArgs;
    sCall += "]";
    OUString sCall = "["
                   + pMethod->GetName()
                   + sQuotedArgs
                   + "]";

    SbxVariable* pRet = pMethod->GetParent()->Execute( sCall );
    if ( pRet && ( pRet != pMethod ) )