on Windows, which includes:

 * Load mysqld.map and insert all symbol/address pairs into hash for
   quick access
 * Resolves all external data variables. The delayloading mechanism
   in MSVC does not support automatic imports of data variables.
   A workaround is to explicitly handle the data import using the delay
   loader during the initialization of the plugin.
 * Resolves all external functions during run-time, by implementing
   the delayed loading helper function delayLoadHelper2, which is
   called by run-time as well as HrLoadAllImportsForDll. 

The delay loader reuses the hash implementation in InnoDB. The normal
hash_create (in hash0hash.c) creates hash tables in buffer pool. But
the delay loader is invoked before the engine is initialized, and 
buffer pools are not ready yet. Instead, the delay loader has its own
implementation of hash_create() and hash_table_free(), called
wdl_hash_create() and wdl_hash_table_free().

This patch should be used with other two patches in order to build
a dynamically linked plugin on Windows:
 * patch for tmpfile functions (r2886)
 * patch for "build" files (to be committed)
 
The list of file changed:

handler/handler0vars.h: new file, defines a list of external data
variables (no external functions).

handler/win_delay_loader.cc: new file, the implementation of the delay
loader for Windows plugin.

handler/ha_innodb.cc: add a header file, and changes for copying the
system variables.

handler/handler0alter.cc: add a header file

handler/i_s.cc: add a header file

rb://27

Reviewed by:	Sunny, Marko
Approved by:	Sunny