build-sys: use non-recursive build

For reasons see excellent paper 'Recursive Make Considered Harmful' by
Peter Miller.

References: http://miller.emu.id.au/pmiller/books/rmch/
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

src/.gitignore

@@ -1,12 +0,0 @@
-gmon.out
-gmon.sum
-*.c.gcov
-*.gcda
-*.gcno
-*~
-*.o
-.deps/
-dhcpd-pools
-Makefile
-Makefile.in
-tags

src/Makemodule.am

@@ -7,12 +7,12 @@ AM_CPPFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/lib -I$(top_builddir)/lib
 dhcpd_pools_LDADD = $(top_builddir)/lib/libdhcpd_pools.la
 
 dhcpd_pools_SOURCES = \
-	analyze.c \
-	defaults.h \
-	dhcpd-pools.c \
-	dhcpd-pools.h \
-	getdata.c \
-	hash.c \
-	other.c \
-	output.c \
-	sort.c
+	src/analyze.c \
+	src/defaults.h \
+	src/dhcpd-pools.c \
+	src/dhcpd-pools.h \
+	src/getdata.c \
+	src/hash.c \
+	src/other.c \
+	src/output.c \
+	src/sort.c