constness fixes

Hi,

created a constness checker, have run against clang source. It dumps a
huge amount of methods which are const (or static) candidates. Take
into consideration that it produces false positives, it is still too
many. Just to picture the status, here are some numbers:

- functions, name 'is*', which can be declared const in clang source: ~100
- functions, name 'get*', which can be declared const in clang source: ~350
- functions, name 'emit*', which can be declared const in clang source: ~250
- total number of methods which can be declared const in clang source: ~3700
- total number of methods which can be declared static in clang source: ~400

- functions, name 'is*', which can be declared const in llvm source: ~150
- functions, name 'get*', which can be declared const in llvm source: ~550
- total number of methods which can be declared const in llvm source: ~1600
- total number of methods which can be declared static in llvm source: ~600

Would you be interested to receive patches to fix them? And which form
would you like to get them?

Regards,
Laszlo

Hi Laszlo,

We are definitely interested in improving Clang codebase. These
changes are conceptually simple and should be easy to review. So
please send patches, but keep them focused (i.e., keep constness
changes separate from any other improvements you did along the way).

Dmitri