tweak fortran pages

code/fortran/Makefile

@@ -0,0 +1,5 @@
+
+INCS = -I/usr/include/plplot -I/usr/lib/x86_64-linux-gnu/fortran/modules/plplot
+
+plplotting:	plplotting.f90 Makefile
+	gfortran -g $< $(INCS) -lplplotfortran -o $@

code/fortran/plplotting.f90

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+program plplotting
+    use plplot
+    implicit none
+
+    call plinit ()
+    call plenv(-2.1, 2.1, -2.1, 2.1, 0, 0)
+    call plend
+end program