gdb: fix manor -> manner typo in some comments

In a recent commit I used 'manor' in some comments rather than
'manner'.  This commit fixes those two mistakes.

I also looked through the gdb/ tree and found one additional instance
of this mistake that this commit also fixes.

gdb/bt-utils.c

@@ -108,7 +108,7 @@ libbacktrace_print (void *data, uintptr_t pc, const char *filename,
   return function != nullptr && strcmp (function, "main") == 0;
 }
 
-/* Write a backtrace to GDB's stderr in an async safe manor.  This is a
+/* Write a backtrace to GDB's stderr in an async safe manner.  This is a
    backtrace of GDB, not any running inferior, and is to be used when GDB
    crashes or hits some other error condition.  */
 

gdb/bt-utils.h

@@ -49,7 +49,7 @@
 #endif
 
 /* Print a backtrace of the current GDB process to the current
-   gdb_stderr.  The output is done in a signal async manor, so it is safe
+   gdb_stderr.  The output is done in a signal async manner, so it is safe
    to call from signal handlers.  */
 
 extern void gdb_internal_backtrace ();

gdb/language.h

@@ -574,7 +574,7 @@ struct language_defn
   /* Return false if the language has first-class arrays.  Return true if
      there are no array values, and array objects decay to pointers, as in
      C.  The default is true as currently most supported languages behave
-     in this manor.  */
+     in this manner.  */
 
   virtual bool c_style_arrays_p () const
   { return true; }