AJIT addon to LLVM 9. + Custom documentation addition

Command used to configure the build

CC=cc CXX=g++ \
   cmake -G Ninja \
     -DCMAKE_EXPORT_COMPILE_COMMANDS=On \
     -DBUILD_SHARED_LIBS=On \
     -DLLVM_ENABLE_ASSERTIONS=On \
     -DLLVM_TARGETS_TO_BUILD="X86;Sparc" \
     -DLLVM_ENABLE_SPHINX=Off \
     -DLLVM_ENABLE_THREADS=On \
     -DLLVM_INSTALL_UTILS=On \
     -DCMAKE_BUILD_TYPE=Debug \
     ../llvm-ajit-git/llvm-ajit