Consolidate Linux connect implementation

This patch consolidates the connect Linux syscall implementation on
sysdeps/unix/sysv/linux/accept.c.  The changes are:

  1. Remove connect from auto-generation syscalls.list on the architecture
     that uses __NR_connect.
  2. Define __NR_connect as default (__ASSUME_CONNECT_SYSCALL) and undef for
     architectures that do not support it.

Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
aarch64-linux-gnu, arm-linux-gnueabihf, and powerpc64le-linux-gnu.

	* sysdeps/unix/sysv/linux/alpha/syscalls.list: Remove connect from
	auto-generation list.
	* sysdeps/unix/sysv/linux/arm/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/generic/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/hppa/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/ia64/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/mips/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/connect.c: Simplify include list.
	* sysdeps/unix/sysv/linux/kernel-features.h
	(__ASSUME_CONNECT_SYSCALL): Define.
	* sysdeps/unix/sysv/linux/i386/kernel-features.h
	(__ASSUME_CONNECT_SYSCALL): Undef if kernel does not support it.
	* sysdeps/unix/sysv/linux/m68k/kernel-features.h
	(__ASSUME_CONNECT_SYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/s390/kernel-features.h
	(__ASSUME_CONNECT_SYSCALL): Likewise.
	* sysdeps/unix/sysv/linux/sparc/kernel-features.h
	(__ASSUME_CONNECT_SYSCALL): Likewise.