Calling directly the omnifunc may move the cursor position. This is the case
with the default Vim omnifunc for C-family languages (ccomplete#Complete) which
calls searchdecl to find a declaration. This function is supposed to move the
cursor to the found declaration but it doesn't when called through the omni
completion mapping (CTRL-X CTRL-O). So, we restore the cursor position after
calling the omnifunc.
Bring fully asynchronous completion by polling for completions with a timer
then calling completefunc once the completions are ready. Use the start column
returned by the server in completefunc. Immediately display the last completion
on the TextChangedI event to prevent the popup menu disappearing while waiting
for the completions. Handle the TextChangedI event not being triggered while
the completion menu is open by closing the menu when inserting a character
through the InsertCharPre event, and when deleting a character on the <BS> and
<C-h> keys.
- OmniCompleter is now more similar to other Completers.
- CompletionRequest doesn't store start_column anymore.
- Calling BuildRequestData only once per request.
