CRoaring | Roaring bitmaps in C with SIMD ( AVX2

The CRoaring library can be amalgamated into a single source file that makes it easier for integration into other projects. Moreover, by making it possible to compile all the critical code into one compilation unit, it can improve the performance. For the rationale, please see the SQLite documentation, https://www.sqlite.org/amalgamation.html, or the corresponding Wikipedia entry (https://en.wikipedia.org/wiki/Single_Compilation_Unit). Users who choose this route, do not need to rely on CRoaring's build system (based on CMake). We maintain pre-generated amalgamated files at https://github.com/lemire/CRoaringUnityBuild for your convenience. To generate the amalgamated files yourself, you can invoke a bash script... (Bash shells are standard under Linux and macOS. Bash shells are available under Windows as part of the  GitHub Desktop under the name Git Shell. So if you have cloned the CRoaring GitHub repository from within the GitHub Desktop, you can right-click on CRoaring, select Git Shell and then enter the above commands.). It is not necessary to invoke the script in the CRoaring directory. You can invoke it from any directory where you want the amalgamation files to be written. It will generate three files for C users: roaring.h, roaring.c and amalgamation_demo.c... as well as some brief instructions. The amalgamation_demo.c file is a short example, whereas roaring.h and roaring.c are "amalgamated" files (including all source and header files for the project). This means that you can simply copy the files roaring.h and roaring.c into your project and be ready to go! No need to produce a library! See the amalgamation_demo.c file.