win,node-gyp: optionally allow node.exe/iojs.exe to be renamed

On Windows, when node or io.js attempts to dynamically load a compiled
addon, the compiled addon tries to load node.exe or iojs.exe again -
depending on which import library the module used when it was linked.
This causes many compiled addons to break when node.exe or iojs.exe are
renamed, because when the binary has been renamed the addon DLL can't
find the (right) .exe file to load its imports from.

This patch gives compiled addon developers an option to overcome this
restriction by compiling a delay-load hook into their binary. The
delay-load hook ensures that whenever a module tries to load imports
from node.exe/iojs.exe, it'll just look at the process image, thereby
making the addon work regardless of what name the node/iojs binary has.

To enable this feature, the addon developer must set the
'win_delay_load_hook' option to 'true' in their binding.gyp file, like
this:

```
{
  'targets': [
    {
      'target_name': 'ernie',
      'win_delay_load_hook': 'true',
      ...
```

Bug: nodejs#751
Bug: nodejs#965
Upstream PR: nodejs/node-gyp#599

PR-URL: nodejs#1251
Reviewed-By: Rod Vagg <[email protected]>

PR-URL: nodejs#1266
Reviewed-By: Ben Noordhuis <[email protected]>