Fix GCC6 -Wmisleading-indentation issues.

Fix GCC6 -Wmisleading-indentation issues.

GCC6 will warn about misleading indentation issues like:

gdb/ada-lang.c: In function ‘ada_evaluate_subexp’:
ada-lang.c:11423:9: error: statement is indented as if it were guarded by...
         arg1 = unwrap_value (arg1);
         ^~~~

gdb/ada-lang.c:11421:7: note: ...this ‘else’ clause, but it is not
       else
       ^~~~

In this case it would be a bug except for the fact the if clause already
returned early. So this misindented statement really only got executed
for the else case. But it could easily mislead a reader, so adding a
proper else block is the correct solution.

In case of c-typeprint.c (c_type_print_base) the if statement is indeed
misleadingly indented, but not a bug. Just indent correctly. The inflow.c
(terminal_ours_1) misindented block comes from the removal of an if clause
in commit d9d2d8b which looks correct. Just introduce an else to fixup the
indentation of the block. The linux-record.c misleadingly indented return
statements are just that. Misleading to the reader, but not actual bugs.
Just unindent them so they don't look like they fall under the wrong if
clause.