[v3] Doxygen improvements for Type Traits and Utilities

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

This patch declares the Type Traits doxygen group in <type_traits> not
in <tr1/type_traits> *and* <tr2/type_traits>. It also makes sure
doxygen comments are attached to the actual trait such as
is_member_pointer, not a helper such as __is_member_pointer_helper.  I
added brief descriptions for some of the less self-explanatory traits
(enable_if, conditional, declval) as well as for std::forward and
altered the std::move comment to say it converts to an rvalue, since
it's not really true to say it moves a value (that depends what the
caller does with the result.)

        * include/std/type_traits: Doxygen improvements.
        * include/bits/move.h: Likewise.
        * include/tr1/type_traits:  Likewise.
        * include/tr2/type_traits:  Likewise.
        * testsuite/20_util/declval/requirements/1_neg.cc: Adjust dg-error
        line numbers
        * testsuite/20_util/forward/c_neg.cc: Likewise.
        * testsuite/20_util/forward/f_neg.cc: Likewise.
        * testsuite/20_util/make_signed/requirements/typedefs_neg.cc:
        Likewise.
        * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc:
        Likewise.

Tested x86-64-linux with "make check" and "make doc-html" - committed to trunk.

Attachment: dox.txt
Description: Text document