Log Message:
firefox{,45,52}: bump pkgrevision with no change.

these packages pull in GCC_REQD+=4.9 via mozilla-common.mk, and
are very widely used (I suspect only www/firefox actually needs it)

this will take care of most of the fallout from major bumping
pkgsrc-gcc-libstdc++ to 7 on netbsd. these are the most widely
used packages setting GCC_REQD>4.8.