Fix joaotavora#361: abide by LSP when reporting and moving to columns

* eglot.el (eglot-current-column-function): Set to
eglot-lsp-abiding-column.
(eglot-move-to-column-function): Set to
eglot-move-to-lsp-abiding-column.

* NEWS.md: Log the change here as well.

Co-authored-by: João Távora <joaotavora@gmail.com>

NEWS.md

@@ -1,5 +1,13 @@
 # 1.6 (upcoming)
 
+##### Column offset calculation is now LSP-conform ([#361][github#361])
+
+It seems the majority of servers now comply with the language server
+specification when it comes to handling non-ASCII texts.  Therefore
+the default values of `eglot-move-to-column-function` and
+`eglot-current-column-function` have been changed.  The documentations
+of these variables help to restore the old behavior.
+
 ##### Support workspace/configuration requests ([#326][github#326])
 
 Also a new section "Per-project server configuration" in the README.md
@@ -205,3 +213,4 @@ and now said bunch of references-->
 [github#316]: https://github.com/joaotavora/eglot/issues/316
 [github#324]: https://github.com/joaotavora/eglot/issues/324
 [github#326]: https://github.com/joaotavora/eglot/issues/326
+[github#361]: https://github.com/joaotavora/eglot/issues/361

eglot.el

@@ -1002,15 +1002,15 @@ CONNECT-ARGS are passed as additional arguments to
 
 (defun eglot-current-column () (- (point) (point-at-bol)))
 
-(defvar eglot-current-column-function #'eglot-current-column
+(defvar eglot-current-column-function #'eglot-lsp-abiding-column
   "Function to calculate the current column.
 
 This is the inverse operation of
 `eglot-move-to-column-function' (which see).  It is a function of
 no arguments returning a column number.  For buffers managed by
 fully LSP-compliant servers, this should be set to
-`eglot-lsp-abiding-column', and `eglot-current-column' (the default)
-for all others.")
+`eglot-lsp-abiding-column' (the default), and
+`eglot-current-column' for all others.")
 
 (defun eglot-lsp-abiding-column ()
   "Calculate current COLUMN as defined by the LSP spec."
@@ -1026,7 +1026,7 @@ for all others.")
          :character (progn (when pos (goto-char pos))
                            (funcall eglot-current-column-function)))))
 
-(defvar eglot-move-to-column-function #'eglot-move-to-column
+(defvar eglot-move-to-column-function #'eglot-move-to-lsp-abiding-column
   "Function to move to a column reported by the LSP server.
 
 According to the standard, LSP column/character offsets are based
@@ -1036,8 +1036,8 @@ where X is a multi-byte character, it actually means `b', not
 `c'. However, many servers don't follow the spec this closely.
 
 For buffers managed by fully LSP-compliant servers, this should
-be set to `eglot-move-to-lsp-abiding-column', and
-`eglot-move-to-column' (the default) for all others.")
+be set to `eglot-move-to-lsp-abiding-column' (the default), and
+`eglot-move-to-column' for all others.")
 
 (defun eglot-move-to-column (column)
   "Move to COLUMN without closely following the LSP spec."