Refactor, replace BSD queue.h LIST_ macros with homegrown version

This patch replaces the BSD doubly linked list implementation with a
simplified homegrown version.  This not only reduces the dependency on
an external "library", but also greatly simplifies licensing and gives
us a clean name space that does not intrude on users who want to use
their own version of queue.h in their application that also includes
the libuEv header file.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/Makefile.am

@@ -11,4 +11,4 @@ bench_LDADD         = libuev.la
 pkgconfigdir        = $(libdir)/pkgconfig
 pkgincludedir       = $(includedir)/uev
 pkgconfig_DATA      = libuev.pc
-pkginclude_HEADERS  = uev.h private.h queue.h
+pkginclude_HEADERS  = uev.h private.h