Native win32 support

Hi,

Here is an update to support win32 natively :) .

Cheers,
Vincent

Unit tests on windows:

```
PS Z:\tmp\node-git> node.exe .\node_modules\nodeunit\bin\nodeunit .\test

test_actor
✔ Should create actor from string seperating name and email
✔ Should create actor from string only containing name
✔ Should correctly return name when calling toString()

test_blame
✔ Should correctly provide simple blame
✔ Should correctly provide deep blame

test_blame_tree
✔ Should correctly retrieve blame tree
✔ Should correctly retrieve blame tree path
✔ Should correctly retrieve blame tree for multiple paths

test_blob
✔ Should not locate blob
✔ Should correctly return blob contents
✔ Should correctly cache data
✔ Should correctly return the file size
✔ Should correctly return mime_type for known types
✔ Should correctly return text plain for unknown types
✔ Should correctly grab the blame
✔ Should correctly return the base name

test_commit
✔ Test commit bake
✔ Test abbreviation of id
✔ Test commit count
✔ Test correct execution of diff
✔ Test diff with two commits
✔ Test diff with files
✔ Test diff with two commits and files
✔ Test diffs
✔ Test diffs on initial import
✔ Test diffs on initial import with empty commit
✔ Test diffs with mode only change
✔ Test toString() override for the commit
✔ Test create patch from commit

test_commit_stats
✔ Should correctly retrieve commit stats
✔ Should correctly match the content

test_commit_write
✔ Should correctly fetch commit index
✔ Should correctly commit all

test_config
✔ Should correctly return an assoc array
✔ Should correctly set value

test_diff
✔ Test list from string new mode

test_file_index
✔ Count all entries
✔ Count for a given sha
✔ Retrieve all files for a commit
✔ Retrieve all commits for a given file
✔ Retrieve array of last commits
✔ Retrieve array of last commits based on regexp pattern
✔ Retrieve last commits containing a directory in array

test_git
✔ Should correctly call native git method
✔ Should fail to call wrong native method
✔ Should fail to call wrong native function with skip timeout
✔ Should correctly transform options
✔ Should correctly escape calls to the git shell
✔ Should correctly escape standalone argument

test_git_alt
✔ Should correctly execute basic
✔ Should correctly work with clone of clone

test_git_basic
✔ Should correctly init gitdir
✔ Should correctly merge logs
✔ Should correctly honor max count
✔ Should correctly retrieve the diff between two commits
✔ Should correctly perform single diff
✔ Should correctly perform full diff
✔ Should correctly perform add diff
✔ Should correctly perform remove diff
✔ Should correctly cat file contents from commit
✔ Should correctly cat file contents from tree
✔ Should correctly cat file contents from blob
✔ Should correctly cat file size
✔ Should correctly execute ls_tree
✔ Should correctly execute ls_tree with blobs
✔ Should correctly execute ls_tree with treeish
✔ Should correctly execute ls_tree with ls_tree_paths
✔ Should correctly execute ls_tree with ls_tree_paths multi single
✔ Should correctly execute ls_tree with recursive
✔ Should correctly execute ls_tree with recursive and a commit
✔ Should correctly execute rev_list pretty
✔ Should correctly execute rev_list raw since
✔ Should correctly execute rev_list raw
✔ Should correctly execute rev_list
✔ Should correctly execute rev_list range
✔ Should correctly execute ls_tree_paths multi
✔ Should correctly execute ls_tree_path
✔ Should correctly execute ls_tree_path deep
✔ Should correctly retrieve file type
✔ Should correctly execute ls_tree and return no sha found tree

test_git_iv2
✔ Should correctly execute basic test
✔ Should correctly test objects

test_head
✔ Should correctly fetch master
✔ Should correctly fetch submaster
✔ Should correctly fetch heads with slashes
✔ Should correctly test is_head function
✔ Should correctly test head count
✔ Should correctly include non-pack

test_index_status
✔ Should correctly add a file
✔ Should correctly add an array
✔ Should correctly remove a file
✔ Should correctly remove an array
✔ Should correctly execute status

test_merge
✔ Should correctly create merge from string

test_raw
✔ Should correctly parse the raw object

test_remote
✔ Should correctly parse the raw object

test_repo
✔ Should update refs packed
✔ Should raise error on invalid repo location
✔ Should raise error on non existing path
✔ Should correctly retrieve the description
✔ Should correctly return array of ref objects
✔ Should correctly return the current head
✔ Should correcty return array of head objects
✔ Should populate head data
✔ Should correctly fetch commits
✔ Should correctly retrieve the commit
✔ Should correctly retrieve the commit count
✔ Should correctly retrieve the repo tree
✔ Should correctly fetch blog instance
✔ Should correctly init bare
✔ Should correctly init bare with options
✔ Should correctly fork_bare
✔ Should correctly do a commit diff
✔ Should correctly locate alternates
✔ Should fail to retrieve alternates
✔ Should correctly set alternates
✔ Should fail to set alternates
✔ Should set empty alternates
✔ Should correctly test log
✔ Should test log with path and options
✔ Should correctly extract commit deltas from nothing new
✔ Should commit deltas from when other has new
✔ Should correctly select existing objects

test_submodule
✔ Should correctly extract the config
✔ Should correctly fetch config with windows lineendings
✔ Should correctly test no config
✔ Should correctly test empty config
✔ Should correctly extract base name

test_tag
✔ Should correctly fetch tag list and have correct string size
✔ Should correctly fetch tag list from string
✔ Should correctly fetch signed tag
✔ Should correctly fetch annotated tag
✔ Should correctly fetch packed tag
✔ Should correctly fetch packed annotated tag

test_tree
✔ Should correctly handle a no tree
✔ Should correctly return a tree from a content to string call
✔ Should correctly return blob from tree from string
✔ Should correctly return submodule from tree from string
✔ Should correctly return error due to invalid type
✔ Should correctly find file in tree
✔ Should correctly test find file with commits
✔ Should correctly extract base name

OK: 500 assertions (123302ms)
```