Integrate with Sarathy.

p4raw-id: //depot/cfgperl@4140

diff --cc perlapi.c
index f04706c,ed7ab92..ed7ab92
mode 100755,100644..100755
--- 1/perlapi.c
--- 2/perlapi.c
+++ b/perlapi.c

diff --cc pod/perldelta.pod
Simple merge

diff --cc pod/perldiag.pod
Simple merge

diff --cc pp_hot.c
Simple merge

diff --cc sv.c
index 892eb6e,b21c9ed..4ba864c
--- 1/sv.c
--- 2/sv.c
+++ b/sv.c
@@@ -5033,12 -5033,23 +5033,25 @@@ Perl_sv_vcatpvfn(pTHX_ SV *sv, const ch
                    dig = uv & 1;
                    *--eptr = '0' + dig;
                } while (uv >>= 1);
 -              if (alt && *eptr != '0')
 -                  *--eptr = '0';
 +              if (alt) {
 +                  esignbuf[esignlen++] = '0';
 +                  esignbuf[esignlen++] = 'b';
 +              }
                break;
            default:            /* it had better be ten or less */
+ #if defined(PERL_Y2KWARN)
+               if (ckWARN(WARN_MISC)) {
+                   STRLEN n;
+                   char *s = SvPV(sv,n);
+                   if (n >= 2 && s[n-2] == '1' && s[n-1] == '9'
+                       && (n == 2 || !isDIGIT(s[n-3])))
+                   {
+                       Perl_warner(aTHX_ WARN_MISC,
+                                   "Possible Y2K bug: %%%c %s",
+                                   c, "format string following '19'");
+                   }
+               }
+ #endif
                do {
                    dig = uv % base;
                    *--eptr = '0' + dig;