[doc] C++ parser interface description bugs

[Jerry Quinn]

Hi, folks.

In the manual for 2.4.1 and 2.4.2, section 10.1.1 indicates that you
need to include %skeleton "lalr1.c" in the parser file to use C++.  This
is actually lalr1.cc.

Section 10.1.4 describes the parser interface for C++.  That page refers
to semantic_value_type and location_value_type, but these are really
semantic_type and location_type.

Thanks,
Jerry Quinn