Motivation: ensure the correct type `IRType` is inferred for definitions
such as
```
def f (n : UInt32) : UInt32 :=
if n == 0 then panic! "foo"
else n+1
```
This is just a draft.
```
for f in `find . -name '*.lean'`; do echo $f; gsed "/^import/s/\b\(.\)/\u\1/g" $f > tmp; gsed "/^Import/s/Import/import/g" tmp > $f; done
```
