added: tests for uninit variable warnings

[Jeffrey A Law]

  In message < 199903120010.TAA03507@blastula.phys.columbia.edu >you write:
  > uninit-4.c is bizarre: the warning goes away if you remove the '1'
  > case, or if you replace 'struct operation' by an int, or even if you
  > make 'struct operation' smaller!  Also, if you take out the default
  > case _and_ the '1' case, the warning goes away, but it shouldn't (what
  > if cpp_lex returns 3?)
Not weird at all.  Changing the numberof cases or density of the switch may
cause the compiler to emit it as a series of cascaded if/else statements which
the compiler is better able to analyze.

Structures also present some interesting problems to the uninitialized
variable analysis.  It's quite a bit more difficult for the compiler to
determine that an entire structure has been initialized as opposed to a simple
integer or floating point variable.


  > The tests are marked XFAIL - all systems.  I'm interested to know if
  > they pass on anyone's machine.
They probably will pass on some machines because of differences in switch
table density threshholds (at least uninit-4)

jeff