Add ability to remove all printf-related functions from a program.

Fixes #33

README.md

@@ -47,6 +47,8 @@ See [advanced_usage.md](advanced_usage.md).
 
 If memory footprint is critical, you can disable library features using compiler definitions. Available controls are:
 
+* `PRINTF_DISABLE_ALL`
+    - Remove all `printf` calls from the program
 * `PRINTF_NTOA_BUFFER_SIZE` (unsigned integer)
     * 'ntoa' conversion buffer size, this must be big enough to hold one converted numeric number including padded zeros (dynamically created on stack)
     * Default: 32 bytes

src/LibPrintf.cpp

@@ -1,4 +1,6 @@
 #include "LibPrintf.h"
+
+#ifndef PRINTF_DISABLE_ALL
 #include "Arduino.h"
 
 #ifdef __AVR__
@@ -25,3 +27,5 @@ extern "C" __attribute__((weak)) void putchar_(char character)
 {
 	print_instance->print(character);
 }
+
+#endif // PRINTF_DISABLE_ALL

src/LibPrintf.h

@@ -1,6 +1,19 @@
 #ifndef ARDUINO_PRINTF_H_
 #define ARDUINO_PRINTF_H_
 
+#ifdef PRINTF_DISABLE_ALL
+
+#define printf(...)
+#define sprintf(...)
+#define vsprintf(...)
+#define snprintf(...)
+#define vsnprintf(...)
+#define vprintf(...)
+
+#define printf_init(...)
+
+#else // printf is enabled
+
 #include "Print.h"
 #include "../extras/printf/printf.h"
 
@@ -24,6 +37,7 @@
 void printf_init(arduino::Print& StreamClass);
 #else
 void printf_init(Print& StreamClass);
-#endif
+#endif // __AVR_ATmega4809__
 
+#endif // PRINTF_DISABLE_ALL
 #endif //ARDUINO_PRINTF_H_