allow itemlist-method's multi-line msgid strings in msgctxt

otherwise pocheck will file on strings like like e.g.

 #: analysis.src
 msgctxt ""
 "analysis.src\n"
 "ANALYSIS_Weeknum\n"
 "Returns the number of the calendar week in which the specified date occurs.\n"
 "This function exists for interoperability with older Microsoft Excel documents, for new documents use WEEKNUM instead.\n"
 "itemlist.text"
 msgid ""
 "Returns the number of the calendar week in which the specified date occurs.\n"
 "This function exists for interoperability with older Microsoft Excel documents, for new documents use WEEKNUM instead."
 msgstr ""

Change-Id: Ib64a989933ca42c5119b0ecf2339f693793d4e96

l10ntools/source/po.cxx

@@ -491,7 +491,6 @@ bool lcl_CheckInputEntry(const GenPoEntry& rEntry)
     const OString sType = sMsgCtxt.copy( nLastDot + 1 );
     return !rEntry.getReference().isEmpty() &&
             nFirstEndLine > 0 &&
-            (nLastEndLine == nFirstEndLine || nLastEndLine == sMsgCtxt.indexOf('\n',nFirstEndLine+1)) &&
             nLastDot - nLastEndLine > 1 &&
             (sType == "text" || sType == "quickhelptext" || sType == "title")&&
             !rEntry.getMsgId().isEmpty();