Allow opening pipe 0 for reading. Useful if it's on a different subnet from others

RF24.cpp

@@ -489,16 +489,16 @@ void RF24::openWritingPipe(uint64_t value)
 void RF24::openReadingPipe(uint8_t child, uint64_t value)
 {
   const uint8_t child_pipe[] = { 
-    RX_ADDR_P1, RX_ADDR_P2, RX_ADDR_P3, RX_ADDR_P4, RX_ADDR_P5   };
+    RX_ADDR_P0, RX_ADDR_P1, RX_ADDR_P2, RX_ADDR_P3, RX_ADDR_P4, RX_ADDR_P5   };
   const uint8_t child_payload_size[] = { 
-    RX_PW_P1, RX_PW_P2, RX_PW_P3, RX_PW_P4, RX_PW_P5   };
+    RX_PW_P0, RX_PW_P1, RX_PW_P2, RX_PW_P3, RX_PW_P4, RX_PW_P5   };
   const uint8_t child_pipe_enable[] = { 
-    ERX_P1, ERX_P2, ERX_P3, ERX_P4, ERX_P5 };
+    ERX_P0, ERX_P1, ERX_P2, ERX_P3, ERX_P4, ERX_P5 };
 
-  if (--child < 5)
+  if (child < 5)
   {
     // For pipes 2-5, only write the LSB
-    if ( !child )
+    if ( child < 2 )
       write_register(child_pipe[child], reinterpret_cast<uint8_t*>(&value), 5);    
     else  
       write_register(child_pipe[child], reinterpret_cast<uint8_t*>(&value), 1);    

RF24.h

@@ -307,7 +307,7 @@ public:
    *
    * @see openWritingPipe
    *
-   * @warning all 5 reading pipes should share the first 32 bits.
+   * @warning Pipes 1-5 should share the first 32 bits.
    * Only the least significant byte should be unique, e.g.
    * 
    * @code
@@ -315,9 +315,9 @@ public:
    *   openReadingPipe(2,0xF0F0F0F066);
    * @endcode
    * 
-   * @todo Enforce the restriction that all pipes must share the top 32 bits
+   * @todo Enforce the restriction that pipes 1-5 must share the top 32 bits
    *
-   * @param number Which pipe# to open, 1-5.
+   * @param number Which pipe# to open, 0-5.
    * @param address The 40-bit address of the pipe to open.
    */
   void openReadingPipe(uint8_t number, uint64_t address);