mesa: Fix setup of LocalParams array.

mesa: Fix setup of LocalParams array.

i965 passed piglit, but swrast and gallium both segfaulted without this.
i965 happened to work because it never ran _mesa_load_state_parameters()
on the new program before the test called glProgramLocalParameter(), which
was allocating a LocalParams array for the fallback path.

v2: Since v1 threw away old localparams data, leaked old LocalParams
    memory, only fixed fragment programs, and I was dubious of my previous
    invariants already (nothing but program_parse.y will generate
    LocalParams, and only that one path of program_parse.y will), just
    late-allocate localparams at the other point of dereferencing them.
    This adds overhead to _mesa_load_state_parameter, which is
    uncomfortable, but I'm pretty sure that giant switch statement is
    super slow already.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71734
Tested-by: Michel Dänzer <michel.daenzer@amd.com>