Reenable TEST_ALL (and #define TEST_FTP in that case)

Reenable TEST_ALL (and #define TEST_FTP in that case)
Fix some warnings about unused functions
Fix asserts coming from incorrect use of GetC(): new wxPutchar asserts when passing a NULL character
Remove TestThreadExec() and MyExecThread: wxExecute can be used only from the main thread
Remove TestFtpWuFtpd: we don't want to test for wu-ftp bugs and ftp.eudora.com doesn't respond anymore
Do not leak the global FTP object

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58094 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775