add note about fractions of a second being allowed with the -i option.
<tag>@C@:</tag> alphabetically by group, module and cost centre.
</descrip>
-<tag>@-i<secs>@:</tag>
-<nidx>-i<secs> RTS option (profiling)</nidx>
-Set the profiling (sampling) interval to @<secs>@ seconds (the
-default is 1~second).
+<tag>@-i<secs>@:</tag> <nidx>-i<secs> RTS option
+(profiling)</nidx> Set the profiling (sampling) interval to @<secs>@
+seconds (the default is 1~second). Fractions are allowed: for example
+@-i0.2@ will get 5 samples per second.
<tag>@-h<break-down>@:</tag>
<nidx>-h<break-down> RTS option (profiling)</nidx>