Makefiles: AM_CPPFLAGS use srcdir

Add $(srcdir) to include paths in AM_CPPFLAGS so that we can
compile the program writing all targets into a directory separate
from the sources.
This is done simply by creatig a subdirectory of the project root
and running "../configure" and "make" inside it.

src/graph/Makefile.am

@@ -3,8 +3,8 @@
 SUBDIRS = generation correlations stats clustering
 
 AM_CPPFLAGS =\
-    -I. -I.. \
-    -I../boost-workaround \
+    -I$(srcdir)/.. \
+    -I$(srcdir)/../boost-workaround \
     -DHAVE_CONFIG_H
 
 AM_CXXFLAGS =\

src/graph/clustering/Makefile.am

 ## Process this file with automake to produce Makefile.in
 
 AM_CPPFLAGS =\
-    -I. -I.. \
-    -I../boost-workaround \
+    -I$(srcdir)/.. \
+    -I$(srcdir)/../../boost-workaround \
     -DHAVE_CONFIG_H
 
 AM_CFLAGS=$(AM_CXXFLAGS)

src/graph/correlations/Makefile.am

 ## Process this file with automake to produce Makefile.in
 
 AM_CPPFLAGS =\
-    -I. -I.. \
-    -I../../boost-workaround \
+    -I$(srcdir)/.. \
+    -I$(srcdir)/../../boost-workaround \
     -DHAVE_CONFIG_H
 
 AM_CFLAGS=$(AM_CXXFLAGS)

src/graph/generation/Makefile.am

 ## Process this file with automake to produce Makefile.in
 
 AM_CPPFLAGS =\
-    -I. -I.. \
-    -I../../boost-workaround \
+    -I$(srcdir)/.. \
+    -I$(srcdir)/../../boost-workaround \
     -DHAVE_CONFIG_H
 
 AM_CXXFLAGS =\

src/graph/stats/Makefile.am

 ## Process this file with automake to produce Makefile.in
 
 AM_CPPFLAGS =\
-    -I. -I.. \
-    -I../boost-workaround \
+    -I$(srcdir)/.. \
+    -I$(srcdir)/../../boost-workaround \
     -DHAVE_CONFIG_H
 
 AM_CFLAGS=$(AM_CXXFLAGS)