Merge pull request #704 from rnpnr/add-vprintf

add Print::vprintf()

teensy4/Print.h

@@ -156,6 +156,8 @@ class Print
 	int printf(const char *format, ...);
 	// printf is a C standard function which allows you to print any number of variables using a somewhat cryptic format string
 	int printf(const __FlashStringHelper *format, ...);
+	// vprintf is a C standard function that allows you to print a variable argument list with a format string
+	int vprintf(const char *format, va_list ap) { return vdprintf((int)this, format, ap); }
 
 	// format warnings are too pedantic - disable until newer toolchain offers better...
 	// https://forum.pjrc.com/threads/62473?p=256873&viewfull=1#post256873