[SETUPLIB] Introduce a lot of (Work in progress) functions to manipulate boot entries...

This concerns so far, only freeldr.ini and to an extent, boot.ini, but planning in the future to add support for registry-oriented BCD
as well as possibly direct (u)EFI entries, using the corresponding NT functions.
This code is so far only used in osdetect.c, but will be soon used by usetup's bootsup.c (note that some helper functions: CreateCommonFreeLdrSections()
and (Un)protectBootIni() are already taken from it and used in bldrsup.c).
- In EnumerateNTOSBootEntries(), continue enumerating the boot entries until the user callback returns an status code that is not successful.
- Remove some old code from osdetect.c; use directly BootEntry->FriendlyName when building the display names of the available installations, since now
  BootEntry->FriendlyName is a PCWSTR (and not a UNICODE_STRING anymore).

svn path=/branches/setup_improvements/; revision=74943

[SETUPLIB] Make the NTOS_BOOT_ENTRY structure more generic, so that it can wrap around either actual NTOS boot entry options, or FreeLdr-like boot-sector options.

In a sense, the NTOS_BOOT_ENTRY structure now looks much more like the NT structure "BOOT_ENTRY".
- Adapt the code in bldrsup.c to these modifications, and re-enable FreeLdr-like boot-sector-file support code that was commented out.
More code cleanup will follow later.

svn path=/branches/setup_improvements/; revision=74952