use std::filesystem::path for filesystem operations

ci/test.lua

@@ -289,12 +289,13 @@ local MODES = {
 
 local function load_test_config(config_file)
     local config = {}
+    print ("loading test config from " .. config_file)
     if dfhack.filesystem.isfile(config_file) then
         config = json.decode_file(config_file)
     end
 
     if not config.test_dir then
-        config.test_dir = dfhack.getHackPath() .. 'scripts/test'
+        config.test_dir = dfhack.getHackPath() .. '/scripts/test'
     end
 
     if not config.save_dir then

docs/changelog.txt

@@ -62,6 +62,7 @@ Template for new versions:
 ## Documentation
 
 ## API
+- ``Filesystem`` module: rewritten to use C++ standard library components, for better portability
 
 ## Lua
 

docs/dev/Lua API.rst

@@ -3168,12 +3168,6 @@ unless otherwise noted.
   specified by ``path``, or -1 if ``path`` does not exist.
   This depends on the system clock and should only be used locally.
 
-* ``dfhack.filesystem.atime(path)``
-* ``dfhack.filesystem.ctime(path)``
-
-  Return values vary across operating systems - return the ``st_atime`` and
-  ``st_ctime`` fields of a C++ stat struct, respectively.
-
 * ``dfhack.filesystem.listdir(path)``
 
   Lists files/directories in a directory.  Returns ``{}`` if ``path`` does not exist.