pg_resetwal: Rename function to avoid potential conflict

ReadControlFile() here conflicts with a function of the same name in
xlog.c.  There is no actual conflict right now, but since
pg_resetwal.c reaches deep inside backend headers, it's possible in
the future.

Discussion: https://www.postgresql.org/message-id/e8f86ba5-48f1-a80a-7f1d-b76bcb9c5c47@2ndquadrant.com

src/bin/pg_resetwal/pg_resetwal.c

@@ -76,7 +76,7 @@ static int	WalSegSz;
 static int	set_wal_segsize;
 
 static void CheckDataVersion(void);
-static bool ReadControlFile(void);
+static bool read_controlfile(void);
 static void GuessControlValues(void);
 static void PrintControlValues(bool guessed);
 static void PrintNewControlValues(void);
@@ -393,7 +393,7 @@ main(int argc, char *argv[])
 	/*
 	 * Attempt to read the existing pg_control file
 	 */
-	if (!ReadControlFile())
+	if (!read_controlfile())
 		GuessControlValues();
 
 	/*
@@ -578,7 +578,7 @@ CheckDataVersion(void)
  * to the current format.  (Currently we don't do anything of the sort.)
  */
 static bool
-ReadControlFile(void)
+read_controlfile(void)
 {
 	int			fd;
 	int			len;