For checking if a symbol >= value, we need to check if symbol == value || symbol
> value. When checking symbol > value and we know that symbol != value, the path
is infeasible only if value == maximum integer.

For checking if a symbol <= value, we need to check if symbol == value || symbol
< value. When checking symbol < value and we know that symbol != value, the path
is infeasible only if value == minimum integer.

Updated test case exercising this logic: we only prune paths if the values are
unsigned.

llvm-svn: 56354

llvm-svn: 56334

  if we know that 'len != 0' and know that 'i == 0' then we know that
  'i < len' must evaluate to true and cannot evaluate to false

llvm-svn: 56260

llvm-svn: 55559

llvm-svn: 55537

llvm-svn: 55536

llvm-svn: 55412