thrift: fix perl module dependencies

[ryandesign (Ryan Carsten Schmidt)]

The perl variant of the thrift port has dependencies on p5-class-accessor and p5-bit-vector. These must be changed to p5.12-class-accessor and p5.12-bit-vector, and the port must be told to use the "perl5.12" program instead of the "perl" program.

(It doesn't have to be 5.12, but it does have to be a specific version of perl, and 5.12 is our current default version.)

[blair (Blair Zajac)]

Fixed in r95289. The port doesn't install the modules in the correct location, but that's a separate issue.