Many minor typo fixes

I ran codespell on gdb/*.[chyl] and fixed a bunch of simple typos.
Most of what remains is trickier, i.e., spots where a somewhat natural
name of something in the code is flagged as a typo.

Reviewed-By: Tom de Vries <tdevries@suse.de>

gdb/ft32-tdep.c

@@ -310,7 +310,7 @@ ft32_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
 		  return sal.end;
 		}
 	    }
-	  /* No useable line symbol.  Use result of prologue parsing method.  */
+	  /* No usable line symbol.  Use result of prologue parsing method.  */
 	  return plg_end;
 	}
     }