AP_HAL: change txspace from a BetterStream method to a Stream method.

libraries/AP_HAL/UARTDriver.h

@@ -60,10 +60,10 @@ public:
     void println_P(const prog_char_t *pstr) {}
     void printf(const char *pstr, ...) {}
     void _printf_P(const prog_char *pstr, ...) {}
-    int txspace() { return 1; }
 
     /* Empty implementations of Stream virtual methods */
     int available() { return 0; }
+    int txspace() { return 1; }
     int read() { return -1; }
     int peek() { return -1; }
 

libraries/AP_HAL/utility/BetterStream.h

@@ -32,9 +32,6 @@ class AP_HAL::BetterStream : public AP_HAL::Stream {
 public:
     BetterStream(void) {}
 
-    // Stream extensions
-    virtual int txspace(void) = 0;
-
     virtual void print_P(const prog_char_t *) = 0; 
     virtual void println_P(const prog_char_t *) = 0;
     virtual void printf(const char *, ...)

libraries/AP_HAL/utility/Stream.h

@@ -11,10 +11,15 @@
 class AP_HAL::Stream : public AP_HAL::Print {
 public:
     virtual int  available() = 0;
+    /* NB txspace was traditionally a member of BetterStream in the
+     * FastSerial library. As far as concerns go, it belongs with available() */
+    virtual int  txspace() = 0;
+
     /* return value for read() and peek() :
      * -1 if nothing available, uint8_t value otherwise. */
     virtual int  read() = 0;
     virtual int  peek() = 0;
+
 };
 
 #endif // __AP_HAL_UTILITY_STREAM_H__

libraries/AP_HAL_AVR/UARTDriver.h

@@ -40,7 +40,6 @@ public:
     }
 
     /* Implementations of BetterStream virtual methods */
-    int txspace();
     void print_P(const prog_char_t *s);
     void println_P(const prog_char_t *s);
     void printf(const char *s, ...)
@@ -50,6 +49,7 @@ public:
 
     /* Implementations of Stream virtual methods */
     int available();
+    int txspace();
     int read();
     int peek();