Add common ASIC/FPGA file formats to GitHub/linguist

[mithro]

Brief explanation

GitHub uses https://github.com/github/linguist to do language stats. Currently the https://github.com/github/linguist/blob/master/lib/linguist/languages.yml file is missing a lot of important file formats used in FPGA/ASIC development.

Of the top of my head;

• [ ] .gds
• [ ] .lib - Liberty timing files
• [ ] .oa - OpenAccess files
• [ ] .spice - Spice simulation files
• [ ] mag, maglef - magic
• [ ] LEF
• [ ] CDL

Commercial file formats;

• [ ] Cadence file format names
• [ ] Calibre file format names

Should check the following are covered too.

• * .v - Verilog (C like -- should use a // comments, supports / / too)
• * .vh - Verilog header (C like -- should use a // comments, supports / / too)
• * .sv - SystemVerilog (should use / / comments, supports / / too)
• * .svh - SystemVerilog header (should use / / comments, supports / / too)
• * .tcl - TCL (should use # comments)
• * .sdc / *.xdc - Synopsis Design Constraint / Xilinx Design Constraint files -- Really TCL scripts (see above)
• .blif/.eblif - Berkley Logic Interface Format (uses bash # style comments)
• .edif - Electronic Design Interchange Format (S-Expressions based -- unknown comment style?)
• .lef - Library Exchange Format (should use # comments)
• .lib - Liberty Timing File (should use / / style comments)
• .sdf - Standard Delay Format (LISP file which supports / / and // comments)
• .spef - Standard parasitics exchange format (supports only // style comments)