ext2fs: quiet compiler warnings

ext2fs: quiet compiler warnings

Include ext2fsP.h in fileio.c for ext2fs_file_block_offset_too_big()
declaration.  Fix up the declaration to mark it extern in the header.

Include <strings.h> header for strcasecmp() in tune2fs.c if available,
as described in the strcasecmp(3) man page, instead of doing this
indirectly by declaring _BSD_SOURCE and getting it from <string.h>.

If CONFIG_QUOTA is undefined, parse_quota_opts() is unused in
tune2fs.c so #ifdef it out.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>