spec: Fix hard-coded image paths

This will probably have no effect in practice, assuming the
target ("web") directory remains at its default location, as the
images would still be available at their old ../images/
location (i.e. dereferencing the source, not the built website).

Author: CyberShadow

spec/contracts.dd

@@ -20,7 +20,7 @@ $(HEADERNAV_TOC)
         $(LI handling of contract inheritance)
         )
 
-$(HTMLTAG3V img, src="../images/d4.gif" style="max-width:100%" alt="Contracts make D bug resistant" border="0")
+$(HTMLTAG3V img, src="$(ROOT_DIR)images/d4.gif" style="max-width:100%" alt="Contracts make D bug resistant" border="0")
 
         $(P The idea of a contract is simple - it's just an expression that must evaluate to true.
         If it does not, the contract is broken, and by definition, the program has a bug in it.

spec/iasm.dd

@@ -6,7 +6,7 @@ $(HEADERNAV_TOC)
 
     $(HTMLTAG3 a,
       href="http://digitalmars.com/gift/index.html" title="Gift Shop" target="_top",
-      $(HTMLTAG3V img, src="../images/d5.gif" border="0" align="right" alt="Some Assembly Required" width="284" height="186")
+      $(HTMLTAG3V img, src="$(ROOT_DIR)images/d5.gif" border="0" align="right" alt="Some Assembly Required" width="284" height="186")
     )
 
     $(P D, being a systems programming language, provides an inline