Upgrade mtools to 3.0.37

This version contains a fix for -Wstring-concatenation error.

Test: presubmit
Bug: 175068488
Change-Id: Id4f2ae49da91a481ab2625fdf17668689b640794
diff --git a/fat_free.c b/fat_free.c
index 6d49018..f7c1d5b 100644
--- a/fat_free.c
+++ b/fat_free.c
@@ -50,7 +50,7 @@
 
 int fatFreeWithDir(Stream_t *Dir, struct directory *dir)
 {
-	unsigned int first;
+	uint32_t first;
 
 	if((!strncmp(dir->name,".      ",8) ||
 	    !strncmp(dir->name,"..     ",8)) &&
@@ -61,7 +61,7 @@
 
 	first = START(dir);
   	if(fat32RootCluster(Dir))
-		first |= STARTHI(dir) << 16;
+		first |= (uint32_t) STARTHI(dir) << 16;
 	return fat_free(Dir, first);
 }
 
@@ -69,4 +69,3 @@
 {
 	return fatFreeWithDir(entry->Dir, &entry->dir);
 }
-