Package for bcl2fastq2 (updates libxslt) (#4234)

* Add v1.1.26 and make crypto a variant

I need 1.1.26 for bcl2fastq2.

I also need to build it without crypto support.

* Initial support for bcl2fastq2

* Clean up commentary, messages, names

No substantial changes intended, just cleanup.

* fix flake8 and extra import

* The masked grammarian strikes again...

* Be normal (messages don't end in periods)

* When +crypto, add --with-crypto

Add `--with-crypto` to configure args when user hasn't explicitly set
`~crypto`.

* self.spec.satisfies is unsatisfying, in is in instead

See #4135, self.spec.satisfies has issues.  @adamjstewart suggests
simply using in.

var/spack/repos/builtin/packages/libxslt/package.py

@@ -36,10 +36,22 @@ class Libxslt(AutotoolsPackage):
     homepage = "http://www.xmlsoft.org/XSLT/index.html"
     url      = "http://xmlsoft.org/sources/libxslt-1.1.28.tar.gz"
 
-    version('1.1.28', '9667bf6f9310b957254fdcf6596600b7')
     version('1.1.29', 'a129d3c44c022de3b9dcf6d6f288d72e')
+    version('1.1.28', '9667bf6f9310b957254fdcf6596600b7')
+    version('1.1.26', 'e61d0364a30146aaa3001296f853b2b9')
+
+    variant('crypto',  default=True,
+            description='Build libexslt with crypto support')
 
     depends_on("libxml2")
     depends_on("xz")
     depends_on("zlib")
-    depends_on("libgcrypt")
+    depends_on("libgcrypt", when="+crypto")
+
+    def configure_args(self):
+        args = []
+        if '~crypto' in self.spec:
+            args.append('--without-crypto')
+        else:
+            args.append('--with-crypto')
+        return args