BaseTools: Support COMPAT16 section generation

BaseTools: Support COMPAT16 section generation

Currently COMPAT16 section type is not recognized and GenSec is called
without the "-s [SectionType]" argument.
Add COMPAT16 type to the SectionType dictionary to fix the issue.

Now this syntax works correctly:
```
FILE FREEFORM = <GUID>  {
  SECTION COMPAT16 = <FILE>
}
```

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>