Fix clang API usage for record / enum link names.

1) Also, emit all mangled symbols for constructors.

2) Add a shared object file parser to libheader-abi-util to filter out
   functions and global variables without DEFAULT or PROTECTED visibility.

3) Update expected tests.

Bug: 62721815

Bug: 62463617

Bug: 62307940

Test: Build libclang with "-UNDEBUG", mm -j64 on external/libcxx

Test: Both C1 and C2 constructors are generated for records.

Change-Id: Id5440a647fe41d27cb857a7d0e06429e28e45d8b