tex2lyx regression bug in branch

[Uwe Stöhr]

Since http://www.lyx.org/trac/changeset/28858/ formulas can no longer be imported to LyX. The reason 
is that in math.cpp the routine

bool is_math_env(string const & name)
{
        return known_math_environments.find(name) != 
known_math_environments.end();
}
now always gives false. I'm not able to find out why. JMarc can you please have 
a look?
Btw. where is the environment list "known_math_environments" stored?

regards Uwe