check -Wformat-security by default since Android does too
fix issue spotted by -Wformat-security
set code style and untabify
write_end must always include offset unless it is in O_APPEND mode

refs #1733 https://dev.guardianproject.info/issues/1733
rename vars in set_value() so they are understandable

end2 is not a clear variable name ;)
expand "offset > existing_size" case to return data written, not bytes

Before, sqlfs_proc_write() was returning the total number of bytes written
when it had to write blank bytes because of offset.  FUSE expects it to
just return how many bytes of actual data it wrote, not the blank stuff too

refs #1733 https://dev.guardianproject.info/issues/1733
when truncating to expand file, set set_value()'s begin/end properly

Somehow these got hard coded to 0/0, which forces the truncate to always
make a zero size file.

fixes #1733 https://dev.guardianproject.info/issues/1733
fix bug when setting end to 0 in set_value()

Setting set_value()'s end value to 0 should mean just write the whole
buffer out, but that logic was broke.