X-Bogosity header not discarded

[Chin Huang]

After upgrading to the latest stable release, I noticed the X-Bogosity
header is no longer discarded from the input.  For example, for the
previous stable release,

% echo 'X-Bogosity: No, tests=bogofilter, spamicity=0.123456, version=0.15.13.1' | old/bogofilter -vvv
X-Bogosity: No, tests=bogofilter, spamicity=0.415000, version=0.15.7
                                     n    pgood     pbad      fw     U
N_P_Q_S_s_x_md                       0  0.00e+00  0.00e+00  4.15e-01
                                        1.00e-02  4.15e-01  0.100

Trying it with the latest stable release,

% echo 'X-Bogosity: No, tests=bogofilter, spamicity=0.123456, version=0.15.13.1' | new/bogofilter -vvv
X-Bogosity: No, tests=bogofilter, spamicity=0.000136, version=0.15.13.1
                                     n    pgood     pbad      fw     U
"0.15.13.1"                          3  0.002737  0.000000  0.001379 +
"head:X-Bogosity"                    3  0.002737  0.000000  0.001379 +
"head:tests"                         5  0.003650  0.000436  0.107230 +
"head:bogofilter"                    4  0.002737  0.000436  0.137967 +
"head:spamicity"                     4  0.002737  0.000436  0.137967 +
"head:version"                      27  0.011861  0.006098  0.339557 +
N_P_Q_S_s_x_md                       6  1.00e+00  5.10e-05  1.36e-04
                                        1.00e-02  4.15e-01  0.100