Use pkginclude_HEADERS for libuEv include files

Fix include file namespace lost in initial conversion to GNU autotools,
use $(prefix)/include/$(PACKAGE)/*.h

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

Makefile.am

@@ -1,7 +1,7 @@
 ACLOCAL_AMFLAGS     = -I m4
 
 lib_LTLIBRARIES     = libuev.la
-include_HEADERS     = uev.h private.h queue.h
+pkginclude_HEADERS  = uev.h private.h queue.h
 libuev_la_SOURCES   = uev.c io.c timer.c signal.c
 
 check_PROGRAMS      = bench