#9 Non-basetype streams should generate better error messages

[Aleksey Nogin]

I've accidentally written "float a<x><y>" where I meant "float a<x,y>"

With v0.5_beta1 this gives:

brcc: brtdecl.cpp:46: BrtStreamType::BrtStreamType(const ArrayType*): Assertion `p->subType->isBaseType()' failed.

with no indication of where in my source code the error is. It would be nice, if the error message was more helpful.