[GCC-XML] Force simulated gcc version

[Brad King]

On 01/15/2013 11:02 AM, Michaël BROUTIN wrote:
> The issue is that GCCXML fails to parse this header, because the
> gcc version defined is too high, so it tries to use std::tr1.

The problem is to distinguish the version of GCC being simulated
and whose interface is being preprocessed from the version of GCC
inside gccxml that is actually used to do the parsing.

Code should treat gccxml just like any other compiler and can use
the __GCCXML__ symbol to identify it.  Boost does this for example:

 http://svn.boost.org/svn/boost/tags/release/Boost_1_52_0/boost/config/select_compiler_config.hpp

 #if defined(__GCCXML__)
 // GCC-XML emulates other compilers, it has to appear first here!
 #   define BOOST_COMPILER_CONFIG "boost/config/compiler/gcc_xml.hpp"

-Brad