Add support for DEC Alpha architecture

[XVilka]

DEC Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA. Alpha was implemented in microprocessors originally developed and fabricated by DEC. These microprocessors were most prominently used in a variety of DEC workstations and servers, which eventually formed the basis for almost all of their mid-to-upper-scale lineup. Several third-party vendors also produced Alpha systems, including PC form factor motherboards.

Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel. The Alpha architecture was sold, along with most parts of DEC, to Compaq in 1998. Compaq, already an Intel customer, phased out Alpha in favor of the forthcoming Hewlett-Packard/Intel Itanium architecture, and sold all Alpha intellectual property to Intel in 2001, effectively killing the product. Hewlett-Packard purchased Compaq later that same year, continuing development of the existing product line until 2004, and selling Alpha-based systems, largely to the existing customer base, until April 2007.

A significant amount of the proprietary and valuable software was created for this platform thus might be of interest for the reverse engineers.

Alpha Architecture Reference Manual

See also rizinorg/rizin#1925

Depends on capstone-engine/capstone#2071