DTrace imposes a 128-byte limit on the length of the function component of
a probe name. When dtrace -G builds up a DOF section for the specified
provider(s), the probe function names are truncated to fit in this limit.
The DOF is later used to build the symbol table for the generated object
file, so the table can end up with truncated references, causing link
errors.

Instead of potentially truncating symbol table entries, write the full
function name to the DOF string table and allow the kernel to enforce the
128-byte function name limit when a process attempts to load its DOF.

PR: 194757
Differential Revision: https://reviews.freebsd.org/D1175
Reviewed by: rpaulo
MFC after: 2 weeks