scribble: render "incremement" and some other chars for Latex/PDF

This change was prompted by the change to DrRacket's "\Delta"
to produce the Unicode "increment" character.

original commit: fc112ccd4627f0b7413ba17a81d050bb840a79b3

collects/mrlib/tex-table.rkt

@@ -92,7 +92,7 @@
     ("Lambda" "Λ")
     ("Sigma" "Σ")
     ("Psi" "Ψ")
-    ("Delta" "Δ")
+    ("Delta" "Δ") ; <- this character is Unicode "increment", not Greek delta
     ("Xi" "Ξ")
     ("Upsilon" "Υ")
     ("Omega" "Ω")