TiffEntry::getString(): can't use ByteStream::peekString().
TiffEntry::getString(): can't use ByteStream::peekString().

Fixes 3 regressions from last commit.
In some cases, the 'strings' may be non-zero-terminated.

LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed,darktable-org/rawspeed,LebedevRI/rawspeed,darktable-org/rawspeed