gcc 4.9.2

Closes #33764.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
gcc: update 4.9.2 bottle.
aget: added head

Additional HEAD to the formula so people can grab the performance fixes
pushed several months ago if desired, given the last stable release was
well… a while ago. Also switched to SHA256 as that is what the aget
website solely displays now.

Closes #33840.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
aget: add 0.4.1 bottle.