This patch makes CPlusPlusLanguage::FindBestAlternateFunctionMangledName local
to CPlusPlusLanguage. We do so by creating a new API CollectAlternateFunctionNames.
Both APIs are called only by IRExecutionUnit. However, by having
FindBestAlternateFunctionMangledName local to the C++ plugin we can
change its implementation in C++-specific ways, which we plan to do
in follow-up commits that add Itanium mangle tree API support to
- API tests still pass