Support UTF-8 and UTF-16 column units - #2000

--- a/linter.py
+++ b/linter.py
@@ -16,25 +16,8 @@
 )
 
 
-def byte_offset_to_index(text, offset):
-    """Return the index in `text` of the character at UTF-8 byte `offset`."""
-    return len(text.encode('utf-8')[:offset].decode('utf-8', 'ignore'))
-
-
-class CppcheckBase(Linter):
-    __abstract__ = True
-
-    def reposition_match(self, line, col, m, vv):
-        if col is not None:
-            # cppcheck reports the column as a byte offset into the UTF-8 line,
-            # so every non-ASCII character before the error shifts it. Sublime
-            # counts characters.
-            col = byte_offset_to_index(vv.select_line(line), col)
-
-        return super().reposition_match(line, col, m, vv)
-
-
-class Cppcheck(CppcheckBase):
+class Cppcheck(Linter):
+    column_unit = 'utf8'
     cmd = CMD
     regex = REGEX
     error_stream = util.STREAM_BOTH  # linting errors are on stderr, exceptions like "file not found" on stdout
@@ -49,7 +32,8 @@
     }
 
 
-class CppcheckPlus(CppcheckBase):
+class CppcheckPlus(Linter):
+    column_unit = 'utf8'
     cmd = CMD
     regex = REGEX
     error_stream = util.STREAM_BOTH  # linting errors are on stderr, exceptions like "file not found" on stdout