fix __cplusplus extern "C" closing brace in pty.h (typo?)

include/pty.h

@@ -12,7 +12,7 @@ int openpty(int *, int *, char *, const struct termios *, const struct winsize *
 int forkpty(int *, char *, const struct termios *, const struct winsize *);
 
 #ifdef __cplusplus
-extern }
+}
 #endif
 
 #endif