patch 8.0.0246: compiler warnings for int to pointer conversion

Problem:    Compiler warnings for int to pointer conversion.
Solution:   Fix macro for mch_memmove(). (John Marriott)
diff --git a/src/version.c b/src/version.c
index a2ebcf5..d3c25e6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    246,
+/**/
     245,
 /**/
     244,
diff --git a/src/vim.h b/src/vim.h
index 1bd3821..abee386 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1715,7 +1715,7 @@
 typedef void	    *vim_acl_T;		/* dummy to pass an ACL to a function */
 
 #ifndef mch_memmove
-# define mch_memmove(to, from, len) memmove((char*)(to), (char*)(from), (char*)(len))
+# define mch_memmove(to, from, len) memmove((char*)(to), (char*)(from), (size_t)(len))
 #endif
 
 /*