[boost] [Graph] What to do about broken compilers?

The graph library has always been in a "barely usable" support on certain compilers (Borland <= 5.6.4 and MSVC 6.0, in particular). The regression tests have always been a mess---Boost 1.31.0 has very few passes for these compilers, and 1.32.0 isn't looking any better. However, the library is somewhat usable, if you stick to a very small subset and don't mind working around INTERNAL COMPILER ERRORs all of the time. What to do? I'm marking the library "unusable" on both compilers, so that we can concentrate our efforts on those compilers that might actually work. Complain loudly, quickly, and preferably with patches if you think this is the wrong approach. Doug