Update license to add LLVM clause for GPLv2 compatibility

Fixes #421
Fixes #169

LICENSE

@@ -175,3 +175,19 @@ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
    of your accepting any such warranty or additional liability.
 
 END OF TERMS AND CONDITIONS
+
+--- Exceptions to the Apache 2.0 License ----
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into an Object form of such source code, you
+may redistribute such embedded portions in such Object form without complying
+with the conditions of Sections 4(a), 4(b) and 4(d) of the License.
+
+In addition, if you combine or link compiled forms of this Software with
+software that is licensed under the GPLv2 ("Combined Software") and if a
+court of competent jurisdiction determines that the patent provision (Section
+3), the indemnity provision (Section 9) or other Section of the License
+conflicts with the conditions of the GPLv2, you may retroactively and
+prospectively choose to deem waived or otherwise exclude such Section(s) of
+the License, but only in their entirety and only with respect to the Combined
+Software.

package.json

@@ -19,7 +19,7 @@
     "events"
   ],
   "author": "Craig Campbell",
-  "license": "Apache-2.0",
+  "license": "Apache-2.0 WITH LLVM-exception",
   "gitHead": "c202a0bd4967d5a3064f9cb376db51dec9345336",
   "readmeFilename": "README.md",
   "devDependencies": {