[SHELL32][SDK] Implement PathIsSlowA and SHSetFolderPathA (#5841)

- Implement PathIsSlowA and SHSetFolderPathA functions.
- Add PathIsSlow and SHSetFolderPath prototypes to <shlobj.h>.
- Fix some <shlobj.h>'s bugs.
- Improve SHOpenPropSheetA function.

dll/win32/shell32/stubs.cpp

@@ -225,13 +225,13 @@ SHGetSetFolderCustomSettingsA(LPSHFOLDERCUSTOMSETTINGSA pfcs,
  */
 BOOL WINAPI
 SHOpenPropSheetW(
-    _In_opt_z_ LPCWSTR pszCaption,
+    _In_opt_ LPCWSTR pszCaption,
     _In_opt_ HKEY *ahKeys,
     _In_ UINT cKeys,
     _In_ const CLSID *pclsidDefault,
     _In_ IDataObject *pDataObject,
     _In_opt_ IShellBrowser *pShellBrowser,
-    _In_opt_z_ LPCWSTR pszStartPage)
+    _In_opt_ LPCWSTR pszStartPage)
 {
     FIXME("SHOpenPropSheetW() stub\n");
     return FALSE;
@@ -1028,24 +1028,11 @@ FirstUserLogon(LPWSTR lpUnknown1, LPWSTR lpUnknown2)
  */
 EXTERN_C HRESULT
 WINAPI
-SHSetFolderPathA(int csidl,
-                 HANDLE hToken,
-                 DWORD dwFlags,
-                 LPCSTR pszPath)
-{
-    FIXME("SHSetFolderPathA() stub\n");
-    return E_FAIL;
-}
-
-/*
- * Unimplemented
- */
-EXTERN_C HRESULT
-WINAPI
-SHSetFolderPathW(int csidl,
-                 HANDLE hToken,
-                 DWORD dwFlags,
-                 LPCWSTR pszPath)
+SHSetFolderPathW(
+    _In_ INT csidl,
+    _In_ HANDLE hToken,
+    _In_ DWORD dwFlags,
+    _In_ LPCWSTR pszPath)
 {
     FIXME("SHSetFolderPathW() stub\n");
     return E_FAIL;
@@ -1089,23 +1076,14 @@ SHShouldShowWizards(LPVOID lpUnknown)
  */
 EXTERN_C BOOL
 WINAPI
-PathIsSlowW(LPCWSTR pszFile, DWORD dwFileAttr)
+PathIsSlowW(
+    _In_ LPCWSTR pszFile,
+    _In_ DWORD dwAttr)
 {
     FIXME("PathIsSlowW() stub\n");
     return FALSE;
 }
 
-/*
- * Unimplemented
- */
-EXTERN_C BOOL
-WINAPI
-PathIsSlowA(LPCSTR pszFile, DWORD dwFileAttr)
-{
-    FIXME("PathIsSlowA() stub\n");
-    return FALSE;
-}
-
 /*
  * Unimplemented
  */