templatize process_socketcall over Arch
templatize process_ipc over Arch
templatize before_syscall_exit over Arch
templatize prepare_socketcall over Arch
templatize prepare_ipc over Arch
tweak comments in {read,write}_bytes_ptrace
fix type of variable storing fallible_ptrace return value
Call Task::rbc_count() to read rbc instead of reading the performance counter directly.

This avoids spurious failures if something has already read and cleared
the hardware rbc counter.
Pass exit code to terminate_recording() and call it when we terminate due to rbc not working.
Fall back to PTRACE_GETFPXREGS when XSAVE is not supported.

Resolves #1282.
Add speculative support for Intell Broadwell microarchitecture.
Treat an unknown rr command word as a request to record that program.

Resolves #1283.
correctly declare epoll_event as packed on x86-64
fix l_{start,len} fields in flock to use off_t
add new wordsize64_defs structure to kernel_abi.h
add x86-64 to supported_arch and define an x86_64_arch