Merge pull request #1623 from alouanchi/patch-1

 Fix Issue 17303 - type error in the href url under the link Systems Programming
merged-on-behalf-of: Vladimir Panteleev <github@thecybershadow.net>

areas-of-d-usage.dd

@@ -12,7 +12,7 @@ $(DIVC page-contents quickindex,
             $(LI $(RELATIVE_LINK2 web, Web applications))
             $(LI $(RELATIVE_LINK2 gui, GUI applications))
         )
-        $(LI $(RELATIVE_LINK2 system_programming, Systems Programming)) $(OL
+        $(LI $(RELATIVE_LINK2 system-programming, Systems Programming)) $(OL
             $(LI $(RELATIVE_LINK2 operating_systems, Operating systems))
             $(LI $(RELATIVE_LINK2 compilers, Compilers))
             $(LI $(RELATIVE_LINK2 embedded, Embedded applications))
@@ -30,7 +30,7 @@ $(DIVC page-contents quickindex,
 
 $(DIVC start-icons,
     $(START_ICONS_ENTRY Industry, industry, industry)
-    $(START_ICONS_ENTRY Systems Programming, gears, systems-programming)
+    $(START_ICONS_ENTRY Systems Programming, gears, system-programming)
     $(START_ICONS_ENTRY Research, flask, cutting-edge)
     $(START_ICONS_ENTRY Academia, graduation-cap, academia)
 )