archivers/pbzip2: Fix fallout on FreeBSD 15+

c++ -O2 -pipe -fstack-protector-strong -fno-strict-aliasing    -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -DUSE_STACKSIZE_CUSTOMIZATION -pthread -D_POSIX_PTHREAD_SEMANTICS  pbzip2.cpp BZ2StreamScanner.cpp ErrorContext.cpppbzip2.cpp BZ2StreamScanner.cpp ErrorContext.cpp -o pbzip2 -lbz2 -lpthread
c++: error: no such file or directory: 'ErrorContext.cpppbzip2.cpp'

While here:
- Replace PORTVERSION with DISTVERSION.
- Switch MASTER_SITES from http to https.
- Update WWW to https://launchpad.net/pbzip2/.

PR:		290004
Approved by:	farrokhi (maintainer)
MFH:		2025Q4
-