Shortcuts execute non-EXE targets

0.4.15-dev-3780-gbf16435-x86-gcc-lin-dbg

Opening a shortcut seems to try and execute the target file regardless of the extension.

The quickest way to replicate this is to open the "Read Me" shortcut on the desktop and watch the debug log for:

(/dll/win32/kernel32/client/proc.c:3417) '\??\X:\reactos\readme.txt': Invalid EXE, and not a batch or script file

This works for more than just the readme. If you rename an executable to an innocuous extension like ".txt" and create a shortcut to it, opening the shortcut will run the disguised program instead of the expected text editor.

The attached patch corrects the behavior of "Run" and shortcuts by checking the file's extension in SHELL_execute before trying to create a process out of it.

https://github.com/reactos/reactos/pull/4363