reiserfs_file_write() casts its (size_t) count parameter to int, which can become
a problem on 64-bit architectures

This attempts to fix this by changing the variables dealing with count
and offset and the "min_t" comparisons to use "size_t" through-out.
Acked-by: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>