git: fix brewed-curl option SSL failures.

Closes #22704.
Closes #22713.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
metaproxy: use boost 1.54

metaproxy was incorrectly linking against boost 1.54.0 despite being
built against 1.49.0, so it was unusable. It appears to be compatible
with 1.54.0 now, however, so just use that instead.
metaproxy: fix typo
serf: build with GSSAPI support.

Brings Kerberos support into Subversion.

Closes #22671.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
serf: update bottle.