fix dumping manpages provided by multiple packages

cmd/xmandump: Fix file flush ordering

cmd/xmandump: Fix compression link targets

cmd/xmandump: support gzip compression

cmd/xmandump/main.go: remove runtime.GC call

Do not force garbage collection in the loop, since that just increases
CPU time with no significant positive effect on memory usage.

cmd/xmandump/main.go: fix unhandled case where existing files caused …

…symlink creation failure

Closes: #9 [via git-merge-pr]

cmd/xmandump/main.go: include symlinks in dump

fixes #7

Closes: #8 [via git-merge-pr]

Update module name and dependencies

Close package file handle as soon as possible

Renamed project, command to xmandump

Closes #2.