wmitime: Update Makefile.
In particular,
- Remove reference to deprecated X11R6 directory.
- Replace FLAGS variable with CFLAGS, CPPFLAGS, and LDFLAGS.
- Honor CC, PREFIX, and DESTDIR variables.
- Use INSTALL instead of cp for installation.
- Remove redundant -lXext flag.
- Move contents of wmitime directory to top directory to ease the building
process.
Inspired in part by the Debian patches [1,2].
[1] http://sources.debian.net/src/wmitime/0.3%
2B20120605-1/debian/patches/20-makefile-CC.patch/
[2] http://sources.debian.net/src/wmitime/0.3%
2B20120605-1/debian/patches/make-install.patch/