Normalize .may_include to always have paths, and paths to include

src/lib/string/.may_include

@@ -6,5 +6,5 @@ lib/malloc/*.h
 lib/ctime/*.h
 lib/string/*.h
 
-strlcat.c
-strlcpy.c
+ext/strlcat.c
+ext/strlcpy.c

src/lib/string/compat_string.c

@@ -14,10 +14,10 @@
 
 /* Inline the strl functions if the platform doesn't have them. */
 #ifndef HAVE_STRLCPY
-#include "strlcpy.c"
+#include "ext/strlcpy.c"
 #endif
 #ifndef HAVE_STRLCAT
-#include "strlcat.c"
+#include "ext/strlcat.c"
 #endif
 
 #include <stdlib.h>