increased solder paste deposits in QFN32-VHHD-2 and QFN32-VHHD-6

Note that QFN28-Atmel and QFN28-SiLabs still need verifying.
QFN28-SiLabs is quite differnt from NXP's specification.

- modules/INFO: added description of solder paste deposit dimensioning
  rules (based on NXP's AN10365)
- modules/qfn.fpd (QFN32-VHHD-2, QFN32-VHHD-6): increased solder paste
  deposits according to the rules

modules/INFO

@@ -24,10 +24,33 @@ F: qfn
 #   http://www.nxp.com/package/SOT617-1.html
 #   http://www.nxp.com/package/SOT617-3.html
 #
+# Solder paste:
+#
+# Footprint    Center pad  Closest NXP (with complete land pattern)
+# QFN28-Atmel  2.4 mm	   for further study
+# QFN28-SiLabs 3.3 mm	   use SiLab's specification
+# QFN32-VHHD-2 3.7 mm	   between SOT818-1 and SOT788-1
+# QFN32-VHHD-6 3.4 mm	   SOT818-1
+#
+# From NXP:
+#
+# Package   Pad  Paste zone  Islands  Isl. size  Isl. gap
+# SiLabs    3.25 3.1	     3 x 3    0.9	 
+# SOT818-1  3.4  1.75	     2 x 2    0.75	 0.25
+# SOT788-1  4.0  2.4	     3 x 3    0.6	 0.3
+#
+# NXP rules (AN10365):
+# - paste zone = 35% of pad area
+# - paste coverge = 20% of pad area
+#
+# Our parameters:
+#
+# Package       Pad  Paste zone  Islands  Isl. size  Isl. gap  Zone  Coverage
+# QFN32-VHHD-2  3.7  2.15	 3 x 3	  0.5	     0.25      34%   20%
+# QFN32-VHHD-6  3.4  1.95	 2 x 2	  0.75	     0.45      33%   19%
+#
 # Known bugs:
 #
-# - we should distribute the solder paste in an array of small
-#   squares instead of just covering the whole center pad.
 # - really ought to merge all the various QFN definitions (we have more
 #   over at gta02-core) into a single QFN file with a big mean table of
 #   everything