result = IsAbsolutePath(p$)
p$ is an absolute path and returns True
if it is or False if it isn't.
Note that this expects the specified path to be in the host's canonical format. Thus, a path like "/home" will be absolute on Linux (among others) but not on AmigaOS where "/home" just refers to a directory named "home" in the parent directory. To convert a path to the host format, you can use MakeHostPath().
True if path is absolute, False otherwise