Log Message:
Update VGAM to version 0.9.1.

Major changes since 0.9.0:

o   A companion package, called \pkg{VGAMdata}, is new.
    Some large data sets previously in \pkg{VGAM} have
    been shifted there, e.g., xs.nz and ugss.
    In \pkg{VGAMdata} there is (new) oly12 and students.tw.
o   pnorm2() argument names have changed from 'sd1' to
    'var1', etc. and 'rho' to 'cov12'.
    See documentation.
    Warning given if it returns any negative value.
o   Introduction of g-type arguments for grid search.
o   Improved initial values for: lomax().
o   Argument 'bred' works for poissonff().
o   latvar() generic available, identical to lv(). But the
    latter will be withdrawn soon.
o   Rank() generic available for RR-VGLMs, QRR-VGLMs, CAO models.
o   New function: pgamma.deriv(), pgamma.deriv.unscaled(),
    vlm2lm.model.matrix().
o   New VGAM family functions:
    posbernoulli.b(), posbernoulli.t(), posbernoulli.tb(tau = 2 or 3).
    These provide estimates of N as well as its standard error.
    Also, truncgeometric() and truncweibull() are new.
    Also, SUR() is new.
    Also, binom2.rho.ss() does not work yet.
o   New argument 'matrix.out = FALSE' for constraints.vlm().
o   cm.vgam() has a few more arguments to provide more flexibility.
    But there should be no changes for VGAM users at this stage.
o   Renamed functions: confint_rrnb() is now renamed to
    Confint.rrnb() and confint_nb1() is now renamed to Confint.nb1().
o   Some changes to component names returned by Confint.rrnb() and
    Confint.nb1(): $CI. and $SE. are uppercase.
o   Some zero-inflated VGAM family functions return a
    "vglm" object with @misc$pstr0 for the estimated
    probability of a structural zero.
o   New data set: olym12.
    Note that Students.tw is earmarked for \pkg{VGAMdata}.
o   Data sets renamed:
    olympic renamed to olym08.
o   Qvar() has a 'which.eta = 1' argument specifying which linear
    predictor to use. So quasi-variances are now
    available to models with M > 1 linear predictors.
o   Tested okay on R 3.0.0.