AP_HAL: require a buffer write() function in all ports

this makes a sufficient performance difference that it is worth it

libraries/AP_HAL/Util.cpp

@@ -15,6 +15,14 @@ public:
             return 0;
         }
     }
+    size_t write(const uint8_t *buffer, size_t size) {
+        size_t n = 0;
+        while (size--) {
+            n += write(*buffer++);
+        }
+        return n;
+    }
+
     size_t _offs; 
     char* const  _str;
     const size_t _size;

libraries/AP_HAL/utility/Print.cpp

@@ -29,16 +29,6 @@
 #include "Print.h"
 using namespace AP_HAL;
 
-/* default implementation: may be overridden */
-size_t Print::write_implementation(const uint8_t *buffer, size_t size)
-{
-  size_t n = 0;
-  while (size--) {
-    n += write(*buffer++);
-  }
-  return n;
-}
-
 size_t Print::print(const char str[])
 {
   return write(str);

libraries/AP_HAL/utility/Print.h

@@ -49,10 +49,9 @@ class AP_HAL::Print {
     Print() {}
 
     virtual size_t write(uint8_t) = 0;
+    virtual size_t write(const uint8_t *buffer, size_t size) = 0;
 
     size_t write(const char *str) { return write((const uint8_t *)str, strlen(str)); }
-    size_t write(const uint8_t *buffer, size_t size) {return write_implementation(buffer, size);}
-    virtual size_t write_implementation(const uint8_t *buffer, size_t size);
   public:
     size_t print(const char[]);
     size_t print(char);