Build fix for the latest LLVMContext changes (LLVM r75445) This shouldn't break the build with older LLVM revs. We include LLVMContext.h in gen/llvm.h now to make the transition a little bit easier.

module bug2;
struct Vec { Vec barf() { return Vec(); } }
class test { this(Vec whee) { } }
void main() { Vec whee; new test(whee.barf()); }