unix: include uv.h in src/version.c
unix: include uv.h in src/version.c

Include uv.h so the compiler sees the right visibility attribute for
uv_version() and uv_version_string().

GYP builds compile with -fvisibility=hidden. Before this commit, the
symbols were not visible in libuv.so.

Fixes joyent/node#5213.

urbit/archaeology2,unknownbrackets/maxcso,urbit/archaeology2,unknownbrackets/maxcso,unknownbrackets/maxcso,urbit/archaeology2,urbit/archaeology2,urbit/archaeology2,unknownbrackets/maxcso,unknownbrackets/maxcso,urbit/archaeology2,urbit/archaeology2,urbit/archaeology2,unknownbrackets/maxcso,unknownbrackets/maxcso,urbit/archaeology2