[analyzer] Create symbol-aware stack hints (building upon r152837).

[analyzer] Create symbol-aware stack hints (building upon r152837).

The symbol-aware stack hint combines the checker-provided message
with the information about how the symbol was passed to the callee: as
a parameter or a return value.

For malloc, the generated messages look like this :
"Returning from 'foo'; released memory via 1st parameter"
"Returning from 'foo'; allocated memory via 1st parameter"
"Returning from 'foo'; allocated memory returned"
"Returning from 'foo'; reallocation of 1st parameter failed"

(We are yet to handle cases when the symbol is a field in a struct or
an array element.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152962 91177308-0d34-0410-b5e6-96231b3b80d8