adding plx::RangeUntilValue

with a small test.
fix integer constant lexing

uint64_t hval = 0xcbf29ce484222325ULL;

Was throwing because we used a signed integer value when we iostream
deserialize it.
small itrange starts_with bug

returning false for a size_t
adding hash_FNV1a

http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param
split FNV1a into 64 and 32 bit versions

Expecting to support 32-bit plex anyhow/
giving up on range conversions adding const_bytes()

and bytes() to ItRange.