Crash with incorrect _Bool->_Bool conversion

So that I don't lose track, posting this testcase here:

_Bool x; int a() {if (x);}

Essentially, EmitScalarConversion is assuming that since the source
and destination types are the same, no conversion is needed, which is
wrong in this case. (Although maybe loading a boolean variable should
immediately truncate it to i1; not sure what the right fix is here.)

-Eli

You're right, we always want bool to be i1 when in a register (even though it can be i8 or i32 in memory), so truncating it is the right fix. I've committed a patch, thanks!

-Chris