Add support for Raspberry Pi 4B

This change make the following commands correctly detect the 4B
however there may be an issue with reading GPIO inputs on the 4B
as they are always returning zero.

The aim of this change is to be the source-equivalent of the binary
package release 2.52[1] which was the last release before upstream
development ceased.

[1] http://wiringpi.com/wiringpi-updated-to-2-52-for-the-raspberry-pi-4b/

wiringPi/wiringPi.h

@@ -102,6 +102,7 @@
 #define	PI_MODEL_3BP 		13
 #define	PI_MODEL_3AP 		14
 #define	PI_MODEL_CM3P 		16
+#define	PI_MODEL_4B 		17
 
 #define	PI_VERSION_1		0
 #define	PI_VERSION_1_1		1
@@ -134,7 +135,7 @@ extern const int   piMemorySize    [ 8] ;
 // wiringPiNodeStruct:
 //	This describes additional device nodes in the extended wiringPi
 //	2.0 scheme of things.
-//	It's a simple linked list for now, but will hopefully migrate to 
+//	It's a simple linked list for now, but will hopefully migrate to
 //	a binary tree for efficiency reasons - but then again, the chances
 //	of more than 1 or 2 devices being added are fairly slim, so who
 //	knows....
@@ -211,7 +212,7 @@ extern          void pwmWrite            (int pin, int value) ;
 extern          int  analogRead          (int pin) ;
 extern          void analogWrite         (int pin, int value) ;
 
-// PiFace specifics 
+// PiFace specifics
 //	(Deprecated)
 
 extern int  wiringPiSetupPiFace (void) ;