Print pcre2test output in colour. (#811)

* Add a --colour flag to pcre2test to colourise the output.
* Comments from the inputfile are in grey (but not those entered in
  interactively)
* All other input is in green
* Messages related to PCRE2 api errors are in magenta
* Messages related to errors with using pcre2test itself are in red
* Timing and memory usage information is in blue
* Normal output is in your terminal's default foreground colour

---------

Co-authored-by: Nicholas Wilson <[email protected]>

Author: IsaacOscar

RunTest

@@ -198,7 +198,7 @@ checkresult()
 checkspecial()
   {
   expect=${2:-0}
-  $sim $valgrind $vjs $pcre2test $1 >>testSoutput
+  $sim $valgrind $vjs $pcre2test $1 >>testSoutput 2>&1
   if [ $? -ne "$expect" ] ; then
     echo "** pcre2test $1 failed - check testSoutput"
     yield=1

doc/html/pcre2test.html

@@ -213,6 +213,12 @@ <h2><a name="SEC4" href="#TOC1">COMMAND LINE OPTIONS</a></h2>
 If an unknown option is given, an error message is output; the exit code is 0.
 </p>
 <p>
+<b>--colo[u]r[=&#60;always,auto,never&#62;]</b>
+By default, the output is coloured if the output file is a terminal (<b>auto</b>).
+Force or suppress output of ANSI colour escapes with <b>always</b> and <b>never</b>
+respectively.
+</p>
+<p>
 <b>-d</b>
 Behave as if each pattern has the <b>debug</b> modifier; the internal
 form and information about the compiled pattern is output after compilation;

doc/pcre2test.1

@@ -179,6 +179,11 @@ information. It returns one of the following values:
 .sp
 If an unknown option is given, an error message is output; the exit code is 0.
 .TP 10
+\fB--colo[u]r[=<always,auto,never>]\fP
+By default, the output is coloured if the output file is a terminal (\fBauto\fP).
+Force or suppress output of ANSI colour escapes with \fBalways\fP and \fBnever\fP
+respectively.
+.TP 10
 \fB-d\fP
 Behave as if each pattern has the \fBdebug\fP modifier; the internal
 form and information about the compiled pattern is output after compilation;