Added public files

Roughly added all public files. Probably missed some, though.
diff --git a/sys/strings.h b/sys/strings.h
new file mode 100644
index 0000000..a78ae1e
--- /dev/null
+++ b/sys/strings.h
@@ -0,0 +1,10 @@
+#ifndef LPC_STRINGS_H_
+#define LPC_STRINGS_H_ 1
+
+/* 'where' argument values for trim() */
+
+#define TRIM_LEFT  0x01
+#define TRIM_RIGHT 0x02
+#define TRIM_BOTH  (TRIM_LEFT|TRIM_RIGHT)
+
+#endif /* LPC_STRINGS_H_ */