[part 1 of WL5655] refactoring dblwr code

rb://861
approved by: Jimmy

* Refactor dblwr code in a separate module
* Cleanup support of pre-4.1 ibuf record format

Author: Inaam Rana

storage/innobase/CMakeLists.txt

@@ -231,6 +231,7 @@ SET(INNOBASE_SOURCES
 	btr/btr0sea.cc
 	buf/buf0buddy.cc
 	buf/buf0buf.cc
+	buf/buf0dblwr.cc
 	buf/buf0checksum.cc
 	buf/buf0dump.cc
 	buf/buf0flu.cc

storage/innobase/buf/buf0buf.cc

@@ -3902,7 +3902,7 @@ buf_page_io_complete(
 			frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
 
 		if (bpage->space == TRX_SYS_SPACE
-		    && trx_doublewrite_page_inside(bpage->offset)) {
+		    && buf_dblwr_page_inside(bpage->offset)) {
 
 			ut_print_timestamp(stderr);
 			fprintf(stderr,