Add Unix Assembly samples

[smola]

Description

Add Unix Assembly samples, including GCC preprocessor syntax. These help
classifying many assembly files (e.g. FreeBSD, OpenBLAS) as Unix
Assembly instead of Motorola 68k Assembly.

• Unix Assembly/support.S
  • Source: https://github.com/freebsd/freebsd/blob/f38c52a875446ee056288f64b33b68cbdb2a46d3/sys/powerpc/powerpc/support.S
  • License: BSD-2-Clause-FreeBSD
• Unix Assembly/gemm_kernel_1x4.S
  • Source: https://github.com/jqlin888/OpenBLAS/blob/30ab84891ced6cb00d402e3be8eec907ed9cc6ee/kernel/x86/gemm_kernel_1x4.S
  • License: BSD-2-Clause

Checklist:

• I am fixing a misclassified language
  • I have included a new sample for the misclassified language: (see description above)
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

[smola]

I'm testing this kind of changes in samples/classifier by doing leave-one-out cross-validation with the following script: https://gist.github.com/smola/18d3477cfe66063a933c7b26f9feb1a6

Using it as follows:

git checkout master
bundle exec ruby cv.rb | sort > a.list
git checkout branch
bundle exec ruby cv.rb | sort > b.list
diff a.list b.list

The difference in this case is the following:

< samples/Unix Assembly/hello.s BAD(Motorola 68K Assembly)
---
> samples/Unix Assembly/gemm_kernel_1x4.S GOOD
> samples/Unix Assembly/hello.s GOOD
> samples/Unix Assembly/support.S GOOD