Use non-literal format for possibly non-standard strftime formats.

Per recent -hackers discussion. The formats in question are %G and %V,
and cause warnings on MinGW at least. We assume the ecpg application
knows what it's doing if it passes these formats to the library.

src/interfaces/ecpg/pgtypeslib/timestamp.c

@@ -501,8 +501,12 @@ dttofmtasc_replace(timestamp * ts, date dDate, int dow, struct tm * tm,
 					 * 4-digit year corresponding to the ISO week number.
 					 */
 				case 'G':
+					{
+						/* Keep compiler quiet - Don't use a literal format */
+						const char *fmt = "%G"; 
+
 						tm->tm_mon -= 1;
-					i = strftime(q, *pstr_len, "%G", tm);
+						i = strftime(q, *pstr_len, fmt, tm);
 						if (i == 0)
 							return -1;
 						while (*q)
@@ -512,6 +516,7 @@ dttofmtasc_replace(timestamp * ts, date dDate, int dow, struct tm * tm,
 						}
 						tm->tm_mon += 1;
 						replace_type = PGTYPES_TYPE_NOTHING;
+					}
 					break;
 
 					/*
@@ -682,7 +687,11 @@ dttofmtasc_replace(timestamp * ts, date dDate, int dow, struct tm * tm,
 					 * decimal number.
 					 */
 				case 'V':
-					i = strftime(q, *pstr_len, "%V", tm);
+					{
+						/* Keep compiler quiet - Don't use a literal format */
+						const char *fmt = "%V"; 
+
+						i = strftime(q, *pstr_len, fmt, tm);
 						if (i == 0)
 							return -1;
 						while (*q)
@@ -691,6 +700,7 @@ dttofmtasc_replace(timestamp * ts, date dDate, int dow, struct tm * tm,
 							(*pstr_len)--;
 						}
 						replace_type = PGTYPES_TYPE_NOTHING;
+					}
 					break;
 
 					/*