sysutils/fusefs-ntfs: clean the port up before functional changes

• Drop needless CPPFLAGS, the build system already knows where to find its bits and pieces by itself
• Replace hand-rolled stripping in the `post-install' target with appropriate INSTALL_TARGET
• In the configure script, treat FreeBSD as first-class operating system and adhere to --with-fuse switch (which we already pass)
• Drop the mount helper-related patch hunk so to not confuse the reader as we also pass it on the CONFIGURE_ARGS explicitly