More umbrella header issues

[Uncommon]

I've tried adding the files that Xcode complains about to ObjectiveGit.modulemap, as in #679, but it doesn't seem to make any difference.

    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/mailmap.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/worktree.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/sys/path.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/sys/alloc.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/deprecated.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/git2/apply.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/path.h'
    /<module-includes>:1:1: Umbrella header for module 'ObjectiveGit' does not include header '/git2/sys/alloc.h'