Apply some minor tweaks to the Visual C++ 2010, 2012, 2013 templates to make
them (layout wise) more consistent with more modern standard files and to
reduce the size of our debug binaries.

This reduces the size of the combined debug .exe files 30% (=60 MB).

* build/generator/templates/vcnet_vcxproj.ezt
  - Generate one property group with a condition instead of many items with
    a condition per item.

  - Enable string pooling in debug builds and disable incremental linking to
    allow dropping unused functions.

  - Drop unused functions while linking in debug builds, but do keep duplicates
    as removing can make debugging hard.
    (E.g. you would see calls into fsx from fsfs when a function wasn't changed
     after copying)


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1582363 13f79535-47bb-0310-9956-ffa450edef68