[clang] [clang][ssaf] Add cpp-bounded-buffers source transformation (PR #210457)

[Ziqing Luo via cfe-commits]

ziqingluo-90 wrote:

@steakhal  I take this PR from Jan. 

I did a major change in addition to addressing comments:

The main change is to narrow the rewrite range:
    
 For pointers, let T mark the spelling of the pointee type according to
 its TypeLoc:
    
 ```
       other-specifiers cv-qualifiers T * other-specifiers pointer-name
                        |--- rewrite ---|
 ```
    
The rewrite range starts at the leading cv-qualifiers and ends at the
STAR of the pointer. other-specifiers before the leading cv-qualifiers
and after the STAR do not belong to the pointee type; they are
therefore left untouched, regardless of whether they are macros or
not.  There should be nothing but trailing cv-qualifiers between T and
the STAR; those cv-qualifiers do belong to the pointee type, so they
are included in the rewrite range.
    
For arrays, let T mark the spelling of the element type according to
its TypeLoc:
    
```
       other-specifiers cv-qualifiers T cv-qualifiers other-specifiers array-name [N]
                        |--------- rewrite ---------|
```
    
The rewrite range starts at the leading cv-qualifiers and ends at the
trailing cv-qualifiers. other-specifiers do not belong to the element
type, so if any token intervenes between T and the trailing
cv-qualifiers, the function fails to find a rewrite range and bails.


https://github.com/llvm/llvm-project/pull/210457