Support `scanf` function

[tyuldashev]

Description
In case code reads user input with scanf UTBot generates wrong regression tests which fails during execution

To Reproduce
Generate tests for following function

int read_with_scanf() {
   int i;

   printf( "Enter a value :");
   scanf("%d", &i);

   return i;
}

Expected behavior
Proper regression tests are generated, which could be successfully executed.

Actual behavior
Generated test fails during execution

TEST(regression, read_with_scanf_test_1)
{
...
    // Expected output
    int expected = -1414812757;

    // Trigger the function
    int actual = read_with_scanf();

    // Check results
    EXPECT_EQ(expected, actual);
}

Additional info
UTBot already supports getchar and getc so expectation is that similar approach could be applied to scanf.