[RFC,v7,05/16] Implement the %OB specifier - alternative month names (bug 10871)

  Some languages (Slavic, Baltic, etc.) require a genitive case of the
month name when formatting a full date (with the day number) while
they require a nominative case when referring to the month standalone.

strftime() now implements a %OB format specifier which generates an
alternative month name.  For those languages %B will return the basic
month name. For those languages which do not use different
(nominative and genitive) cases of the month name or do not yet have
their locales updated %OB will retrieve the same string as %B so
moving to %OB will be harmless as long as the version of glibc which
supports this feature is used.

Note that it is not yet decided whether %OB will return the
standalone case (usually nominative) and %B will return the full
date context case (usually genitive) or vice versa.  It depends
on the locale database and localized format strings which may vary
with the locales and depend on what a language community decides.

strptime() now accepts both nominative and genitive month names.

[BZ #10871]
* time/strftime_l.c: %OB format for alternative month names added.
* time/strptime_l.c: alternative month names also recognized.
---
 time/strftime_l.c | 11 +++++++++--
 time/strptime_l.c | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

 # define HERE_AM_STR (_nl_C_LC_TIME.values[_NL_ITEM_INDEX (AM_STR)].string)
@@ -403,6 +405,20 @@ __strptime_internal (const char *rp, const char *fmt,
struct tm *tmp,
 	      if (s.decided !=raw)
 		{
 		  trp = rp;
+#ifdef _LIBC
+		  /* First check the alt month.  */
+		  if (match_string (_NL_CURRENT (LC_TIME, ALTMON_1 + cnt), trp)
+		      && trp > rp_longest)
+		    {
+		      rp_longest = trp;
+		      cnt_longest = cnt;
+		      if (s.decided == not
+			  && strcmp (_NL_CURRENT (LC_TIME, ALTMON_1 + cnt),
+				     alt_month_name[cnt]))
+			decided_longest = loc;
+		    }
+		  trp = rp;
+#endif
 		  if (match_string (_NL_CURRENT (LC_TIME, MON_1 + cnt), trp)
 		      && trp > rp_longest)
 		    {
@@ -429,6 +445,10 @@ __strptime_internal (const char *rp, const char *fmt,
struct tm *tmp,
 	      if (s.decided != loc
 		  && (((trp = rp, match_string (month_name[cnt], trp))
 		       && trp > rp_longest)
+#ifdef _LIBC
+		      || ((trp = rp, match_string (alt_month_name[cnt], trp))
+			  && trp > rp_longest)
+#endif
 		      || ((trp = rp, match_string (ab_month_name[cnt], trp))
 			  && trp > rp_longest)))
 		{
@@ -1016,6 +1036,10 @@ __strptime_internal (const char *rp, const char *fmt,
struct tm *tmp,
 	case 'O':
 	  switch (*fmt++)
 	    {
+	    case 'B':
+	      /* Undo the increment and continue.  */
+	      fmt--;
+	      break;
 	    case 'd':
 	    case 'e':
 	      /* Match day of month using alternate numeric symbols.  */