make bitcoin include files more modular

src/strlcpy.h

@@ -13,7 +13,8 @@
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
-
+#ifndef BITCOIN_STRLCPY_H
+#define BITCOIN_STRLCPY_H
 /*
  * Copy src to string dst of size siz.  At most siz-1 characters
  * will be copied.  Always NUL terminates (unless siz == 0).
@@ -82,3 +83,4 @@ inline size_t strlcat(char *dst, const char *src, size_t siz)
 
     return(dlen + (s - src)); /* count does not include NUL */
 }
+#endif