Fix a few oversights in the longer cancel keys patch

Change MyCancelKeyLength's type from uint8 to int. While it always
fits in a uint8, plain int is less surprising, as there's no
particular reason for it to be uint8.

Fix one ProcSignalInit caller that passed 'false' instead of NULL for
the pointer argument.

Author: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://www.postgresql.org/message-id/61be9e31-7b7d-49d5-bc11-721800d89d64@eisentraut.org

src/backend/postmaster/auxprocess.c

@@ -66,7 +66,7 @@ AuxiliaryProcessMainCommon(void)
 
 	BaseInit();
 
-	ProcSignalInit(false, 0);
+	ProcSignalInit(NULL, 0);
 
 	/*
 	 * Auxiliary processes don't run transactions, but they may need a

src/backend/utils/init/globals.c

@@ -51,7 +51,7 @@ TimestampTz MyStartTimestamp;
 struct ClientSocket *MyClientSocket;
 struct Port *MyProcPort;
 char		MyCancelKey[MAX_CANCEL_KEY_LENGTH];
-uint8		MyCancelKeyLength = 0;
+int			MyCancelKeyLength = 0;
 int			MyPMChildSlot;
 
 /*

src/include/miscadmin.h

@@ -193,7 +193,7 @@ extern PGDLLIMPORT TimestampTz MyStartTimestamp;
 extern PGDLLIMPORT struct Port *MyProcPort;
 extern PGDLLIMPORT struct Latch *MyLatch;
 extern PGDLLIMPORT char MyCancelKey[];
-extern PGDLLIMPORT uint8 MyCancelKeyLength;
+extern PGDLLIMPORT int MyCancelKeyLength;
 extern PGDLLIMPORT int MyPMChildSlot;
 
 extern PGDLLIMPORT char OutputFileName[];