Originating from Xilinx/HLS_arbitrary_Precision_Types commit 200a9ae.

Keeping these headers separate from our other Tools headers for two reasons.

1. They originated from somewhere else and have a different (although very permissive) license.
2. They do not pass our strigent compilation requirements so we have CMake pretend they are system headers.

The Apache 2 license requires us to publish the changes we've made to the source code we have copied. This requirement is satisifed by keeping our commits to ldmx-sw public. The other requirement is keeping the Apache 2 license on the copied source code which we can maintain by keeping this code separate.

The original README is available as well.