Commit r210360 removed the first "i" field from the various instruction
nodes in rtx.def, moving it to an explicit "int insn_uid;" field
of the union "u2" within rtx_def.
Update the comment in rtl.def to reflect this change. Also, fix
a stray apostrophe.
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu
OK for trunk?
gcc/ChangeLog:
* rtl.def: Update comment for "things in the instruction chain" to
reflect the removal of the leading "i" field for INSN_UID in
r210360. Fix bogus apostrophe.