Update configuration for new working draft N4878 and add correspondin…

…g Editors' Report N4879

Update configuration for new working draft N4868 and add corresponding

Editors' Report N4867.

[tab:container.alloc.req] Indent clauses to fix the build.

N4861 Post-Prague 2020 C++ working draft

N4849 Pre-Prague 2020 C++ working draft.

N4842 Post-Belfast 2019 C++ working draft.

Update configuration to build new working draft N4835.

Add new papers N4835 and N4836 (Editors' Report).

Update configuration to build new working draft N4830.

Add new papers N4830 and N4829 (Editors' Report).

Update configuration to build new working draft N4820.

Add new papers N4820 and N4821 (Editors' Report).

Update configuration to build new working draft N4810.

Add new papers N4810 and N4811 (Editors' Report).