EXO: Refactored text input interface into its own file

Moved text_input_manager_v1 interface into another file,
to be followed by refactoring of more protocols.

Refactor wayland_text_input_delegate.* from server.cc
with no new code.

Modify server_util to add more utilities

Bug: 896710
Test: Compiled on ChromeOS.
Change-Id: I2739c538a16640fdaebed1cd7493d300dd42a5a9
Reviewed-on: https://chromium-review.googlesource.com/c/1306406
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Shawn Gallea <sagallea@google.com>
Cr-Commit-Position: refs/heads/master@{#607738}
6 files changed