This patch fixes compiling xpaint inside a gentoo prefix.
There are multiple issues:
	search paths hardcoded to /usr/include,
	install paths outside prefix,
	X resources in app-defaults with path hardcoded to /usr/share/xpaint
--- a/Makefile.am
+++ b/Makefile.am
@@ -3,7 +3,7 @@
 ## Local Configuration arguments
 BINDIR = $(prefix)/bin
 SHAREDIR = $(prefix)/share/xpaint
-XAPPLOADDIR = /etc/X11/app-defaults
+XAPPLOADDIR = $(sysconfdir)/X11/app-defaults
 
 ## Enable/disable PRINTCAP (for older BSD style printing configuration)
 ## PRINTCAP = -DPRINTCAP
@@ -85,7 +85,7 @@
 .PHONY:
 
 version.h:
-	rm -f xaw_incdir ; ln -s /usr/include/X11/Xaw3dxft xaw_incdir
+	rm -f xaw_incdir ; ln -s @includedir@/X11/Xaw3dxft xaw_incdir
 	echo "#define XPAINT_VERSION \"$(PACKAGE_VERSION)\"" > version.h
 
 substads: substads.c
@@ -149,8 +149,7 @@
 	mkdir -p $(DESTDIR)$(SHAREDIR)/messages
 	cd share/messages ; $(RM) -f *~ ; cp -f Messages* $(DESTDIR)$(SHAREDIR)/messages
 	chmod -R a+r $(DESTDIR)$(SHAREDIR)/
-	cd util ; make install
-	cd vxp2ps ; make install
+	cd vxp2ps ; make BINDIR=$(BINDIR) install
 
 clean-local:
 	rm -f xaw_incdir
--- a/util/Makefile
+++ b/util/Makefile
@@ -17,9 +17,9 @@
 
 ifneq ($(WITH_PGF),no)
 pgf2pnm: main.cpp pnm.cpp
-	@if [ -x /usr/include/libpgf ] ; then \
-	$(CXX) $(CXXFLAGS) -fpermissive -c main.cpp -o main.o -I/usr/include/libpgf ; \
-	$(CXX) $(CXXFLAGS) -fpermissive -c pnm.cpp -o pnm.o -I/usr/include/libpgf ; \
+	@if [ -x $(includedir)/libpgf ] ; then \
+	$(CXX) $(CXXFLAGS) -fpermissive -c main.cpp -o main.o -I$(includedir)/libpgf ; \
+	$(CXX) $(CXXFLAGS) -fpermissive -c pnm.cpp -o pnm.o -I$(includedir)/libpgf ; \
 	$(CXX) $(CXXFLAGS) -fpermissive -o pgf2pnm main.o pnm.o $(LDFLAGS) -lpgf ; \
 	else \
 	echo "libpgf not installed !!" ; \
--- a/configure.ac
+++ b/configure.ac
@@ -32,7 +32,7 @@
 AC_TYPE_UINT32_T
 AC_TYPE_UINT64_T
 
-CFLAGS="$CFLAGS -I/usr/include -I/usr/include/X11 -I/usr/include/X11/Xaw3dxft"
+CFLAGS="$CFLAGS -I${prefix}/include -I${prefix}/include/X11 -I${prefix}/include/X11/Xaw3dxft"
 LIBS="$LIBS -lm"
 echo "VERSION = $VERSION" > .version
 
@@ -40,7 +40,7 @@
 AC_CHECK_LIB([X11], [XOpenDisplay], have_x11="yes")
 if test x"$have_x11" = xyes; then
   AC_SUBST([X_LIBS], ["-lXmu -lXt -lSM -lICE -lXext -lX11 -lXpm -ldl -rdynamic"])
-  AC_SUBST([X_CFLAGS], ["-I/usr/include/X11"])
+  AC_SUBST([X_CFLAGS], ["-I${prefix}/include/X11"])
 else
   echo "X11 libraries not installed !"
   exit 1
@@ -291,7 +291,7 @@
 fi
 
 if test x$enable_libopenjp2 = xyes; then
-  CFLAGS="$CFLAGS -I/usr/include/openjpeg-2.3"
+  CFLAGS="$CFLAGS -I${prefix}/include/openjpeg-2.3"
   LIBS="$LIBS -lopenjp2"
   AC_SUBST(LIBOPENJP2_LIBS)
   AC_DEFINE(HAVE_OPENJP2)
@@ -323,9 +323,9 @@
   [AC_LANG_PROGRAM([[#include <freetype2/config/ftheader.h>]])],
   [AC_MSG_RESULT([already in path])],
   [AC_PREPROC_IFELSE(
-    [AC_LANG_PROGRAM([[#include </usr/include/freetype2/freetype/config/ftheader.h>]])],
-    [AC_MSG_RESULT([/usr/include/freetype2])
-     AC_SUBST([SPECIAL_CFLAGS], ["-I/usr/include/freetype2"])],
+    [AC_LANG_PROGRAM([[#include <${prefix}/include/freetype2/freetype/config/ftheader.h>]])],
+    [AC_MSG_RESULT([${prefix}/include/freetype2])
+     AC_SUBST([SPECIAL_CFLAGS], ["-I${prefix}/include/freetype2"])],
     [AC_MSG_ERROR([cannot find freetype2 headers; try setting CFLAGS.])]
   )]
 )
--- a/xpaintrw/Makefile.am
+++ b/xpaintrw/Makefile.am
@@ -13,7 +13,7 @@
 ARCH_DEFINES = -fPIC
 
 ## PBM_DEFINES = -DNETPBM10
-PBM_DEFINES = -I/usr/include/netpbm -DNETPBM11
+PBM_DEFINES = -I@includedir@/netpbm -DNETPBM11
 
 ## 
 ## Specific xpaint options