Add protections against infrared divergences.  Now B22 and B1 return
0.0 if p == m1 == m2 == 0.  This is the default behaviour of
LoopTools:

  $ ./lt
   Usage:  lt `parameters' [versionkey]
   computes the n-point one-loop integrals
   n depends on `parameters':
     n = 1: m
     n = 2: p m1 m2
     n = 3: p1 p2 p1p2 m1 m2 m3
     n = 4: p1 p2 p3 p4 p1p2 p2p3 m1 m2 m3 m4
     n = 5: p1 p2 p3 p4 p5 p1p2 p2p3 p3p4 p4p5 p5p1 m1 m2 m3 m4 m5
   versionkey can be one of:
     0 = compute version a (same as no versionkey)
     1 = compute version b
     2 = compute a and b, compare, return a
     3 = compute a and b, compare, return b

  $ ./lt 0 0 0
   ====================================================
     FF 2.0, a package to evaluate one-loop integrals
   written by G. J. van Oldenborgh, NIKHEF-H, Amsterdam
   ====================================================
   for the algorithms used see preprint NIKHEF-H 89/17,
   'New Algorithms for One-loop Integrals', by G.J. van
   Oldenborgh and J.A.M. Vermaseren, published in
   Zeitschrift fuer Physik C46(1990)425.
   ====================================================
   Bcoeff           1
     p     =   0.0000000000000000
     m1    =   0.0000000000000000
     m2    =   0.0000000000000000
   bb0     = (  0.0000000000000000     ,  0.0000000000000000     )
   bb1     = (  0.0000000000000000     ,  0.0000000000000000     )
   bb00    = (  0.0000000000000000     ,  0.0000000000000000     )
   bb11    = (  0.0000000000000000     ,  0.0000000000000000     )
   bb001   = (  0.0000000000000000     ,  0.0000000000000000     )
   bb111   = (  0.0000000000000000     ,  0.0000000000000000     )
   dbb0    = (  0.0000000000000000     ,  0.0000000000000000     )
   dbb1    = (  0.0000000000000000     ,  0.0000000000000000     )
   dbb00   = (  0.0000000000000000     ,  0.0000000000000000     )
   dbb11   = (  0.0000000000000000     ,  0.0000000000000000     )
   ====================================================

  total number of errors and warnings
  ===================================
  fferr: no errors