Fix installation of headers with parallel install.

The pkginclude was not fully implemented in src/Makefile* and that leaded
to creation $(includedir)/libfm instead of symlink.

src/Makefile.am

@@ -153,11 +153,13 @@ libfm_gtk_SOURCES = \
 	gtk/fm-thumbnail.c \
 	$(NULL)
 
+# we use common include directory for all headers
+pkgincludedir = $(includedir)/@PACKAGE@-@FMLIBVER@
+
 if EXTRALIB_ONLY
 pkginclude_HEADERS = $(LIBFM_EXTRA_INCLUDES)
 else
-libfmincludedir = $(includedir)/@PACKAGE@-@FMLIBVER@
-libfminclude_HEADERS = \
+LIBFM_INCLUDES = \
 	fm.h \
 	fm-seal.h \
 	base/fm-app-info.h \
@@ -194,8 +196,7 @@ libfminclude_HEADERS = \
 	job/fm-simple-job.h \
 	$(NULL)
 
-libfmgtkincludedir = $(includedir)/@PACKAGE@-@FMLIBVER@
-libfmgtkinclude_HEADERS = \
+LIBFM_GTK_INCLUDES = \
 	fm-gtk.h \
 	gtk/fm-app-chooser-combo-box.h \
 	gtk/fm-app-chooser-dlg.h \
@@ -236,8 +237,7 @@ pkginclude_HEADERS = \
 	$(NULL)
 endif
 
-libfmextraincludedir = $(includedir)/@PACKAGE@-@FMLIBVER@
-libfmextrainclude_HEADERS = \
+LIBFM_EXTRA_INCLUDES = \
 	fm-extra.h \
 	fm-version.h \
 	extra/fm-xml-file.h \