Add commented out test timings to test files.

[glennj]

Something like

#!/usr/bin/env tclsh
package require tcltest
namespace import ::tcltest::*

# Uncommenting the next line will display the duration of each test 
#configure -verbose {error body usec}

source testHelpers.tcl

Without that configure command, the sieve exercise testing looks like

$ RUN_ALL=true ./sieve.test
sieve.test:     Total   5       Passed  5       Skipped 0       Failed  0

With it:

$ RUN_ALL=true ./sieve.test
++++ sieve-1 took 243 μs
++++ sieve-2 took 67 μs
++++ sieve-3 took 31 μs
++++ sieve-4 took 31 μs
++++ sieve-5 took 398 μs
sieve.test:     Total   5       Passed  5       Skipped 0       Failed  0