Remove last lambda from context.c

This might actually change the behavior of pconfigure, but it isn't
doing so in any of my test cases so hopefully that means it's OK...
Actually remove last lambda from context.c

I missed a duplicated one.
Remove lambda.h entirely

With any luck this should now build on OSX!
Remove lambda-specific compiler flags

These are no longer necessary because we no longer have lambda calls!
Add "-t" to "mktemp -d"

This seems to be necessary on OSX.