Update Clang download in INSTALL.md for FC (#732)
Update Clang download in INSTALL.md for FC (#732)

FC23 and FC24 need Clang 3.9.0 because of ABI changes in the C++
runtime library. Split the installation instructions to FC22 and
FC23/24.
iovisor/bcc,mcaleavya/bcc,mkacik/bcc,tuxology/bcc,mcaleavya/bcc,romain-intel/bcc,romain-intel/bcc,mkacik/bcc,brendangregg/bcc,tuxology/bcc,mcaleavya/bcc,shodoco/bcc,shodoco/bcc,mkacik/bcc,shodoco/bcc,mkacik/bcc,tuxology/bcc,iovisor/bcc,shodoco/bcc,brendangregg/bcc,tuxology/bcc,shodoco/bcc,iovisor/bcc,romain-intel/bcc,mcaleavya/bcc,tuxology/bcc,romain-intel/bcc,brendangregg/bcc,brendangregg/bcc,mcaleavya/bcc,mkacik/bcc,iovisor/bcc,romain-intel/bcc,brendangregg/bcc,iovisor/bcc