[2.5] generic_usercopy() function

Hello all,

especially the Video4Linux-driver rely intensively on the video_usercopy() function, which handles the copying of userspace arguments of ioctls with a simply callback mechanism.

Recently the dvb-core has been added which needs the same function. Because of the fact that the core is independent of Video4Linux, the code was duplicated to a dvb_usercopy() function.

In order to prevent this code duplication, introducing a generic_usercopy() function to lib/ is one possibilty.

The appended 4 patches do the following:

01-introduce.diff:
- remove video_usercopy() from videodev.c
- add generic_usercopy() to "lib/usecopy.c" and update the build system

02-video.diff:
- change all users of video_usercopy() to use generic_usercopy() instead

03-radio.diff:
- change all users of video_usercopy() to use generic_usercopy() instead

04-dvb.diff
- remove dvb_usercopy() from the dvb core and fix it to use generic_usercopy() instead.

The diffs are against 2.5.69.

Comments are very appreciated. 8-)
Is there a possibility to get this into the kernel?

CU
Michael.