C,C++: fix properties field for object defined or declared with structure definitions

[masatake]

With this pull request, ctags can fill properties: field of svar and fn in the input like:

static struct S { ... } svar;
static struct T { ... } fn(...) { ... }

The declaration like:

static struct T { ... } fn(...);

is not in the scope of this pull request because of the bug reported in #3943.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.38%. Comparing base (8706976) to head (89e16c5).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3944 +/- ## ======================================= Coverage 85.38% 85.38% ======================================= Files 234 234 Lines 56202 56204 +2 ======================================= + Hits 47987 47989 +2 Misses 8215 8215 ```

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