Fix a misspelling: undefied -> undefined

lib/libc_r/man/pthread_exit.3

@@ -70,7 +70,7 @@ it. The function's return value serves as the thread's exit status.
 .Pp
 The behavior of
 .Fn pthread_exit
-is undefied if called from a cancellation handler or destructor function
+is undefined if called from a cancellation handler or destructor function
 that was invoked as the result of an implicit or explicit call to
 .Fn pthread_exit .
 .Pp

lib/libpthread/man/pthread_exit.3

@@ -70,7 +70,7 @@ it. The function's return value serves as the thread's exit status.
 .Pp
 The behavior of
 .Fn pthread_exit
-is undefied if called from a cancellation handler or destructor function
+is undefined if called from a cancellation handler or destructor function
 that was invoked as the result of an implicit or explicit call to
 .Fn pthread_exit .
 .Pp

share/man/man3/pthread_exit.3

@@ -70,7 +70,7 @@ it. The function's return value serves as the thread's exit status.
 .Pp
 The behavior of
 .Fn pthread_exit
-is undefied if called from a cancellation handler or destructor function
+is undefined if called from a cancellation handler or destructor function
 that was invoked as the result of an implicit or explicit call to
 .Fn pthread_exit .
 .Pp