availableForWrite() return int

Author: hathach

cores/nRF5/Print.h

@@ -58,7 +58,7 @@ class Print
 
     // default to zero, meaning "a single write may block"
     // should be overriden by subclasses with buffering
-    virtual size_t availableForWrite() { return 0; }
+    virtual int availableForWrite() { return 0; }
 
     size_t print(const __FlashStringHelper *);
     size_t print(const String &);