[SETUPLIB] Code re-organization in bootsup.c and fsutil.c.

- Move the actual VBR bootcode installation helpers into fsutil.c
  (they depend on the selected filesystem).

- Introduce InstallBootCodeToDisk() and InstallBootCodeToFile()
  and bootcode.c helpers, in order to replace the several functions
  that were duplicating the same code.

base/setup/lib/fsutil.h

@@ -3,7 +3,7 @@
  * LICENSE:     GPL-2.0+ (https://spdx.org/licenses/GPL-2.0+)
  * PURPOSE:     Filesystem support functions
  * COPYRIGHT:   Copyright 2003-2019 Casper S. Hornstrup (chorns@users.sourceforge.net)
- *              Copyright 2017-2019 Hermes Belusca-Maito
+ *              Copyright 2017-2020 Hermes Belusca-Maito
  */
 
 #pragma once
@@ -61,6 +61,42 @@ FormatFileSystem(
     IN PFMIFSCALLBACK Callback);
 
 
+//
+// Bootsector routines
+//
+
+#define FAT_BOOTSECTOR_SIZE     (1 * SECTORSIZE)
+#define FAT32_BOOTSECTOR_SIZE   (1 * SECTORSIZE) // Counts only the primary sector.
+#define BTRFS_BOOTSECTOR_SIZE   (3 * SECTORSIZE)
+
+typedef NTSTATUS
+(/*NTAPI*/ *PFS_INSTALL_BOOTCODE)(
+    IN PCWSTR SrcPath,          // Bootsector source file (on the installation medium)
+    IN HANDLE DstPath,          // Where to save the bootsector built from the source + partition information
+    IN HANDLE RootPartition);   // Partition holding the (old) bootsector data information
+
+NTSTATUS
+InstallFat1216BootCode(
+    IN PCWSTR SrcPath,
+    IN HANDLE DstPath,
+    IN HANDLE RootPartition);
+
+#define InstallFat12BootCode    InstallFat1216BootCode
+#define InstallFat16BootCode    InstallFat1216BootCode
+
+NTSTATUS
+InstallFat32BootCode(
+    IN PCWSTR SrcPath,
+    IN HANDLE DstPath,
+    IN HANDLE RootPartition);
+
+NTSTATUS
+InstallBtrfsBootCode(
+    IN PCWSTR SrcPath,
+    IN HANDLE DstPath,
+    IN HANDLE RootPartition);
+
+
 //
 // Formatting routines
 //