UTBot cannot run test for old-style declared function

[tyuldashev]

Description
In case 'C' method used 'old-style' declaration UTBot does not properly generate '.h' file and later cannot compile it for test execution.

To Reproduce
Steps to reproduce the behavior:

• Generate code for following method

int sum(a, b)
int a;
int b;
{
    return a + b;
}

• The generated tests in '.cpp' file looks pretty normal
• Try to run generated tests

Expected behavior
Tests are supposed to be executed.

Actual behavior
Execution fails with error: "1 actions failed during building and running tests." . Log contains following errors:

In file included from /home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.cpp:5:
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:63:37: error: unknown type name 'a'
extern "C" int sum_src_old_syntax_c(a, b);
                                    ^
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:63:40: error: unknown type name 'b'
extern "C" int sum_src_old_syntax_c(a, b);
                                       ^
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:64:16: error: unknown type name 'a'
static int sum(a, b) {
               ^
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:64:19: error: unknown type name 'b'
static int sum(a, b) {
                  ^
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:65:29: error: use of undeclared identifier 'a'
return sum_src_old_syntax_c(a, b);
                            ^
/home/utbot/remote/SampleDocker2/tests/makefiles/src/../../../tests/src/old_syntax_dot_c_test.h:65:32: error: use of undeclared identifier 'b'
return sum_src_old_syntax_c(a, b);
                               ^
6 errors generated.
....

That's because generated header file for test has following declaration:

extern "C" int sum_src_old_syntax_c(a, b);
static int sum(a, b) {
return sum_src_old_syntax_c(a, b);
}

Additional information
Please note that even this syntax is not widely used in modern applications it could be found in old, but still active projects. For instance I found it in zlib library (2k Forks, 3.9k Start on GitHub, 40 commits in last month). So I believe that we should not put this case on hold.