llCastRay() is currently not available on the grid. It has been introduced some time ago on
Le Tigre and
Magnum beta servers, but is listed as: "
llCastRay() function included but disabled. "
However, v1.26.0.16 will list the new LSL functions and constants that have been
introduced on last Tuesday's rolling restart.
Note that even if not "officially" listed by the viewer (i.e. not highlighted and documented in the script editor window), the new functions and constants always compile fine on servers supporting them, and work just fine too as long as they are server side functions (they almost all are); exceptions to the "work just fine too" are functions such as llTextBox() and constants such as
AGENT_AUTOPILOT which require viewer-side code to work (and both llTextBox() and AGENT_AUTOPILOT are supported by the Cool VL Viewer). Note that the "media on a prim" functions fall into this category (objects using them will currently not work with any v1-based viewer: this will change when media on a prim will get backported to them, which may happen sometime in the future (after Mesh backport and probably after multi-layered clothes support) for the Cool VL Viewer).