Integer overflow in solana_rbpf

From version 0.2.14 to 0.2.16 for Solana rBPF, function "relocate" in the file src/elf.rs has an integer overflow bug because the sym.st_value is read directly from ELF file without checking. If the sym.st_value is rather large, an integer overflow is triggered while calculating the variable "addr" via "addr = (sym.st_value + refd_pa) as u64";