Fixed loading localised resources.

We weren't loading the correct resources for non-English languages when
compiled as a Unicode application.

We now explicitly call FindResourceEx(), LoadResource() and
CreateDialogIndirectParam() to ensure the appropriate windows are shown.

We now explicitly pass GetUserDefaultLangID() to FormatMessage(),
falling back to language neutral if it fails.

Resources and messages are now explicitly UTF-16LE.  That means that git
will treat them as binary and refuse to diff them.  To work around that,
add the following to .git/info/attributes:

    *.mc diff=utf16
    *.rc diff=utf16

and the following to .git/config:

    [diff "utf16"]
    	textconv = "iconv -f utf-16le -t utf-8"