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]

Codecov Report

All modified and coverable lines are covered by tests ✅

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

Additional details and impacted files

@@           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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