unsigned char param to drawChar(), thanks MoFoQ!

Adafruit_GFX.cpp

@@ -368,7 +368,7 @@ void Adafruit_GFX::write(uint8_t c) {
 }
 
 // draw a character
-void Adafruit_GFX::drawChar(int16_t x, int16_t y, char c,
+void Adafruit_GFX::drawChar(int16_t x, int16_t y, unsigned char c,
 			    uint16_t color, uint16_t bg, uint8_t size) {
 
   if((x >= _width)            || // Clip right

Adafruit_GFX.h

@@ -66,7 +66,7 @@ class Adafruit_GFX : public Print {
   void drawBitmap(int16_t x, int16_t y, 
 		  const uint8_t *bitmap, int16_t w, int16_t h,
 		  uint16_t color);
-  void drawChar(int16_t x, int16_t y, char c,
+  void drawChar(int16_t x, int16_t y, unsigned char c,
 		uint16_t color, uint16_t bg, uint8_t size);
 #if ARDUINO >= 100
   virtual size_t write(uint8_t);