Don't build wxFileSystemWatcher test if wxUSE_FSWATCHER==0.

Closes #16031.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76028 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix Intel compiler warnings about hiding member variables.

Rename method parameters to avoid conflicts with member variables names.

Closes #15971.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76029 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Allow passing NULL buffer to wx{,F}File::{Read,Write} when count==0.

If the count of bytes to read or write is 0, the buffer pointer value
shouldn't matter as it's not used at all anyhow, so relax the assert and allow
it to be NULL in this case.

Closes #16018.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76030 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775