Essentially adds the Everest .h and .c files to the various variables. This
should be generalized at some point, but there is no infrastructure for this
yet.
These files are automatically generated by the Everest toolchain from F*
files. They do not respect the mbedTLS code style guidelines as manual
modification would invalidate verification guarantees. The files in
3rdparty/everest/include/kremli{n,b} are a customized (minimzed) version of the
support headers expected by the code extracted using KreMLin.
