[PATCH] On Windows: support install layout of sasl

[Alexandr Miloslavskiy <al...@syntevo.com>]

When I'm building SVN, I like to make/install all dependencies and then 
use these "installed" folders to build svn. Unfortunately SVN doesn't 
recognize installed layout for SASL dependency. Let's fix that.

[[
On Windows: support install layout of sasl

Source layout of sasl has include headers here:
/include

However, when sasl is installed, it has headers here:
/include/sasl

This patch adds auto-detection of layout to support both.

* build/generator/gen_win_dependencies.py
   (_find_sasl): Detect layout in provided '--with-sasl='
* include/private/ra_svn_wrapped_sasl.h
   Support installed layout
]]