vfs: add tryunlink method
Thoughout hg code, we see a pattern of attempting to remove a file and then
catching and ignoring any errors due to a missing file in the calling code.
Let's unify this pattern in a single implementation in the vfs layer.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true