Create serf 1.3 support for Windows backport branch

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x-serf-1.3+-windows@1517122 13f79535-47bb-0310-9956-ffa450edef68
Allow building Subversion 1.8.x against Serf 1.3.0 and higher by allowing
compilation against an already compiled zlib and serf for this specific
scenario.

Compiling serf requires an already compiled zlib, so we can't just (re)compile
zlib after serf.

On trunk this is handled via the improved library detection code.

* build/generator/gen_win.py
  Drop 'serf' and 'zlib' targets for serf >= 1.3.0
  Link against libeay32 and ssleay32 for serf >= 1.3.0
  Fix zlib library name when using an already compiled zlib.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x-serf-1.3+-windows@1517123 13f79535-47bb-0310-9956-ffa450edef68
Merge ^/subversion/branches/1.8.x-serf-1.3+-windows from trunk manually,
because our automatic merge script doesn't like the branch name.

 * ^/subversion/branches/1.8.x-serf-1.3+-windows
   Allow compiling against serf 1.3 and later on Windows
   Justification:
     Serf 1.3 brings a lot of fixes that we need for 1.8.x stability.
   Notes:
     The dependency handling on Windows was updated for 1.9+, so this
     needs a specific backport patch (r1517123)
   Votes:
     +1: rhuijben, brane, stefan2
     
../trunk/tools/dist/backport.pl: sh(256):  (in 'the 1.8.x-serf-1.3+-windows branch') at
../trunk/tools/dist/backport.pl line 258, <STATUS> chunk 21.
Warning summary
===============

1.8.x-serf-1.3+-windows (^/subversion/branches/1.8.x-serf-1.3+-windows[...]): sh(256): 



git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1533874 13f79535-47bb-0310-9956-ffa450edef68