patch 8.1.1414: alloc() returning "char_u *" causes a lot of type casts

Problem:    Alloc() returning "char_u *" causes a lot of type casts.
Solution:   Have it return "void *". (Mike Williams)  Define ALLOC_ONE() to
            check the simple allocations.
diff --git a/src/normal.c b/src/normal.c
index cee90d4..1ff9297 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -5655,7 +5655,7 @@
 	    vim_free(buf);
 	    return;
 	}
-	newbuf = (char_u *)vim_realloc(buf, STRLEN(buf) + STRLEN(p) + 1);
+	newbuf = vim_realloc(buf, STRLEN(buf) + STRLEN(p) + 1);
 	if (newbuf == NULL)
 	{
 	    vim_free(buf);