Fix two bugs in format-string checking:
(1) Do not assume the data arguments start after the format string
(2) Do not use the fact that a function is variadic to treat it like a va_list printf function

Fixes PR 6697.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99480 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed