Suppress unused-variable warnings when building with ICU 4.2.

Tidy-up for commit eccead9e.

src/backend/commands/collationcmds.c

@@ -678,14 +678,30 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 		 */
 		for (i = -1; i < ucol_countAvailable(); i++)
 		{
+			/*
+			 * In ICU 4.2, ucol_getKeywordsForLocale() sometimes returns
+			 * values that will not be accepted by uloc_toLanguageTag().  Skip
+			 * loading keyword variants in that version.  (Both
+			 * ucol_getKeywordValuesForLocale() and uloc_toLanguageTag() are
+			 * new in ICU 4.2, so older versions are not supported at all.)
+			 *
+			 * XXX We have no information about ICU 4.3 through 4.7, but we
+			 * know the code below works with 4.8.
+			 */
+#if U_ICU_VERSION_MAJOR_NUM > 4 || (U_ICU_VERSION_MAJOR_NUM == 4 && U_ICU_VERSION_MINOR_NUM > 2)
+#define LOAD_ICU_KEYWORD_VARIANTS
+#endif
+
 			const char *name;
 			char	   *langtag;
 			char	   *icucomment;
 			const char *collcollate;
+			Oid			collid;
+#ifdef LOAD_ICU_KEYWORD_VARIANTS
 			UEnumeration *en;
 			UErrorCode	status;
 			const char *val;
-			Oid			collid;
+#endif
 
 			if (i == -1)
 				name = "";		/* ICU root locale */
@@ -721,18 +737,9 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 			}
 
 			/*
-			 * Add keyword variants
-			 *
-			 * In ICU 4.2, ucol_getKeywordsForLocale() sometimes returns
-			 * values that will not be accepted by uloc_toLanguageTag().  Skip
-			 * loading keyword variants in that version.  (Both
-			 * ucol_getKeywordValuesForLocale() and uloc_toLanguageTag() are
-			 * new in ICU 4.2, so older versions are not supported at all.)
-			 *
-			 * XXX We have no information about ICU 4.3 through 4.7, but we
-			 * know the below works with 4.8.
+			 * Add keyword variants, if enabled.
 			 */
-#if U_ICU_VERSION_MAJOR_NUM > 4 || (U_ICU_VERSION_MAJOR_NUM == 4 && U_ICU_VERSION_MINOR_NUM > 2)
+#ifdef LOAD_ICU_KEYWORD_VARIANTS
 			status = U_ZERO_ERROR;
 			en = ucol_getKeywordValuesForLocale("collation", name, TRUE, &status);
 			if (U_FAILURE(status))
@@ -779,7 +786,7 @@ pg_import_system_collations(PG_FUNCTION_ARGS)
 						(errmsg("could not get keyword values for locale \"%s\": %s",
 								name, u_errorName(status))));
 			uenum_close(en);
-#endif							/* ICU >4.2 */
+#endif							/* LOAD_ICU_KEYWORD_VARIANTS */
 		}
 	}
 #endif							/* USE_ICU */