Fix an improperly placed comma.

Doc/lib/libprofile.tex

@@ -616,7 +616,7 @@ t = t[0] + t[1] - self.t  # no calibration constant
 You can also achieve the same results using a derived class (and the
 profiler will actually run equally fast!!), but the above method is
 the simplest to use.  I could have made the profiler ``self
-calibrating'', but it would have made the initialization of the
+calibrating,'' but it would have made the initialization of the
 profiler class slower, and would have required some \emph{very} fancy
 coding, or else the use of a variable where the constant \samp{.00053}
 was placed in the code shown.  This is a \strong{VERY} critical