docs: add acctst cli reference imported from CAref.html

modules/ca/src/client/Makefile

@@ -12,6 +12,7 @@ TOP = ../../../..
 include $(TOP)/configure/CONFIG
 
 HTMLS += CAref.html
+DOCS += acctst.md
 
 #
 #	includes to install from this subproject

modules/ca/src/client/acctst.md

@@ -0,0 +1,18 @@
+# acctst
+
+    acctst <PV name> [progress logging level] [channel duplication count]
+                     [test repetition count] [enable preemptive callback]
+
+## Description
+
+Channel Access Client Library regression test.
+
+The PV used with the test must be native type `DBR_DOUBLE` or `DBR_FLOAT`,
+and modified only by acctst while the test is running. Therefore,
+periodically scanned hardware attached analog input records do not work
+well. Test failure is indicated if the program stops prior to printing
+"test complete". If unspecified the progress logging level is zero,
+and no messages are printed while the test is progressing. If
+unspecified, the channel duplication count is 20000. If unspecified, the
+test repetition count is once only. If unspecified, preemptive callback
+is disabled.