Improve GDB's baseclass detection with typedefs

Improve GDB's baseclass detection with typedefs

When a class inherits from a typedef'd baseclass, GDB may be unable to
find the baseclass if the user is not using the typedef'd name, as is
tested on gdb.cp/virtbase2.exp; the reason that test case is working
under gcc is that the dwarf generated by gcc links the class to the
original definition of the baseclass, not to the typedef.  If the
inheritance is linked to the typedef, such as how clang does it,
gdb.cp/virtbase2.exp starts failing.

This can also be seen in gdb.cp/impl-this.exp, when attempting to print
D::Bint::i, and GDB not being able to find the baseclass Bint.

This happens because searching for baseclasses only uses the macro
TYPE_BASECLASS_NAME, which returns the typedef'd name. However, we can't
switch that macro to checking for typedefs, otherwise we wouldn't be
able to find the typedef'd name anymore. This is fixed by searching for
members or baseclasses by name, we check both the saved name and the
name after checking for typedefs.

This also fixes said long-standing bug in gdb.cp/impl-this.exp when the
compiler adds information about typedefs in the debuginfo.