File plugin never watches file changes using inotify

[Kyzer]

FilePlugin.cs and Daemon.cs use #if LINUX or #if LINUX || MACOSX conditional sections to decide whether or not to use the Inotify daemon.

Firstly, the inotify-specific code should be using HAVE_INOTIFY. Only the Linux/MAC OS X specific code (e.g. UNIX signal handling) should use LINUX or MACOSX defines.

Secondly, the decision about platform made in configure.ac is not propagated to the compiled code. The LINUX define is unconditionally set for the main Tangerine assembly - it's always set by the MCS_FLAGS line in Tangerine/Makefile.am, and also in Tangerine/Tangerine.csproj for a debug build, but never set for the File plugin assembly. MACOSX is never set anywhere.

I've created a patch against the development branch of Tangerine that fixes both these issues, and also prints a log warning if HAVE_INOTIFY is not defined.