patch 9.0.1725: cursor pos wrong after concealed text with 'virtualedit'

Problem:    Wrong cursor position when clicking after concealed text
            with 'virtualedit'.
Solution:   Store virtual columns in ScreenCols[] instead of text
            columns, and always use coladvance() when clicking.

This also fixes incorrect curswant when clicking on a TAB, so now
Test_normal_click_on_ctrl_char() asserts the same results as the ones
before patch 9.0.0048.

closes: #12808

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/globals.h b/src/globals.h
index 6a68c3a..c1e2d6f 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -32,7 +32,7 @@
  * The characters that are currently on the screen are kept in ScreenLines[].
  * It is a single block of characters, the size of the screen plus one line.
  * The attributes for those characters are kept in ScreenAttrs[].
- * The byte offset in the line is kept in ScreenCols[].
+ * The virtual column in the line is kept in ScreenCols[].
  *
  * "LineOffset[n]" is the offset from ScreenLines[] for the start of line 'n'.
  * The same value is used for ScreenLinesUC[], ScreenAttrs[] and ScreenCols[].