Generate docs

bin/clang-tblgen -gen-diag-docs -I../clang/include \
          -I../clang/include/clang/Basic/ \
          ../clang/include/clang/Basic/Diagnostic.td -o \
          ../clang/docs/DiagnosticsReference.rst && \
    bin/clang-tblgen -gen-attr-docs -I../clang/include \
            ../clang/include/clang/Basic/Attr.td -o \
            ../clang/docs/AttributeReference.rst && \
    bin/clang-tblgen -gen-opt-docs -I../clang/include \
            -I../clang/include/clang/Driver -I../llvm/include \
            ../clang/include/clang/Driver/ClangOptionDocs.td -o \
            ../clang/docs/ClangCommandLineReference.rst