ports-mgmt/pkg: update to 2.7.1

Major Changes:

• install: respect -q
• vital: now explicitly state the SAT solver issue are due to a vital package
• lua: add pkg.exec_capture, a pkg.exec version capturing stdout/stderr
• Honor --repository flag for disabled repos as documented

Other Changes:

• version: add IGNORE_MAJOR to pkg.conf and document it
• pkg_config: accept int as boolean converted via != 0
• lock: do not error in expected (un)lock state
• backup_libraries: now fully respects rootdir
• backup libraries: atomic replacement of the library
• DB: loudly complain if the DB cannot be opened
• shlibs: also remove ignored shlibs provided from shlibs required