Fix for db-btree.t failures

[Kevin Walker]

I didn't see anything about this in the archives, so...

In order to make the db-btree test work, first change

     #!./perl -w
     BEGIN {
           @INC = '../lib';

to

     #!./perl -w
     BEGIN {
           @INC = '../../lib';

in the file db-btree.t.  After this change, all tests passed until:

    ...
    ok 89
    ok 90
    ok 91
    *** malloc[16098]: error for object 0x156a30: Incorrect check sum for
        freed object - object was probably modified after beeing freed; break
         at szone_error
    ok 92
    Segmentation fault

After removing tests 89-91 (not 92!), tests 1-88 and 92-157 all passed.