Fix the comparison between opaque parameters

Function parameters can be opaque and have no size information. For
example, __va_list in AArch64 ABI. header-abi-diff considers opaque
types compatible if their mangled names are the same.

The mangled name of __va_list can be _ZTI9__va_list or _ZTISt9__va_list.
They are also compatible.

Test: ./test.py
Bug: 248418092
Change-Id: I812abcabb620301eb575c54c7e3d2ff63dade488
8 files changed