Fixed configure.ac to use $CC instead of 'gcc' for version checking.
Fixed configure.ac to use $CC instead of 'gcc' for version checking.

This has caused problems in settings where the desired compiler
isn't the system bundled GCC (as in Mac OS X Mavericks builds where
we have been using specific versions of GCC).

Review #14164 is re-enabled for $(CC) instead of 'gcc' and lets us
compile with GCC 4.8 on Mavericks instead of down-grading to 4.7.

From: Niklas Nielsen <9f210bbd62dc30b7ba6fb21f85df5244526c4049@qni.dk>
Review: https://reviews.apache.org/r/15193

gsantovena/mesos,kaysoky/mesos,verizonlabs/mesos,neilconway/mesos,reneploetz/mesos,kaysoky/mesos,gsantovena/mesos,chhsia0/mesos,gsantovena/mesos,Gilbert88/mesos,zmalik/mesos,chhsia0/mesos,craimbert/mesos,asamerh4/mesos,yuquanshan/customizedMesos,andschwa/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,reneploetz/mesos,asamerh4/mesos,Gilbert88/mesos,kaysoky/mesos,chhsia0/mesos,reneploetz/mesos,jpeach/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,craimbert/mesos,dforsyth/mesos,gsantovena/mesos,abudnik/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,jpeach/mesos,craimbert/mesos,andschwa/mesos,reneploetz/mesos,dforsyth/mesos,dforsyth/mesos,dforsyth/mesos,abudnik/mesos,chhsia0/mesos,zmalik/mesos,jpeach/mesos,andschwa/mesos,neilconway/mesos,zmalik/mesos,yuquanshan/customizedMesos,neilconway/mesos,chhsia0/mesos,andschwa/mesos,Aman-Jain-14/customizedMesos,abudnik/mesos,craimbert/mesos,asamerh4/mesos,andschwa/mesos,abudnik/mesos,zmalik/mesos,andschwa/mesos,abudnik/mesos,kaysoky/mesos,craimbert/mesos,jpeach/mesos,chhsia0/mesos,jpeach/mesos,craimbert/mesos,neilconway/mesos,andschwa/mesos,verizonlabs/mesos,Gilbert88/mesos,zmalik/mesos,verizonlabs/mesos,Gilbert88/mesos,kaysoky/mesos,Gilbert88/mesos,Gilbert88/mesos,asamerh4/mesos,reneploetz/mesos,craimbert/mesos,yuquanshan/customizedMesos,kaysoky/mesos,abudnik/mesos,yuquanshan/customizedMesos,jpeach/mesos,gsantovena/mesos,reneploetz/mesos,kaysoky/mesos,dforsyth/mesos,abudnik/mesos,neilconway/mesos,dforsyth/mesos,reneploetz/mesos,yuquanshan/customizedMesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,zmalik/mesos,dforsyth/mesos,asamerh4/mesos,neilconway/mesos,verizonlabs/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,asamerh4/mesos,jpeach/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,verizonlabs/mesos,asamerh4/mesos