Fix CAPTURE macro for nontrivial uses

The previous implemetation was just plain broken for most of
possible uses, the new one should work (even though it is ugly
as all hell, and should be improved ASAP).

Fixes #1436

docs/logging.md

@@ -57,20 +57,37 @@ The message is reported and the test case fails.
 
 AS `FAIL`, but does not abort the test
 
-## Quickly capture a variable value
+## Quickly capture value of variables or expressions
 
-**CAPTURE(** _expression_ **)**
+**CAPTURE(** _expression1_, _expression2_, ... **)**
 
-Sometimes you just want to log the name and value of a variable. While you can easily do this with the INFO macro, above, as a convenience the CAPTURE macro handles the stringising of the variable name for you (actually it works with any expression, not just variables).
+Sometimes you just want to log a value of variable, or expression. For
+convenience, we provide the `CAPTURE` macro, that can take a variable,
+or an expression, and prints out that variable/expression and its value
+at the time of capture.
 
-E.g.
-```c++
-CAPTURE( theAnswer );
+e.g. `CAPTURE( theAnswer );` will log message "theAnswer := 42", while
+```cpp
+int a = 1, b = 2, c = 3;
+CAPTURE( a, b, c, a + b, c > b, a == 1);
+```
+will log a total of 6 messages:
+```
+a := 1
+b := 2
+c := 3
+a + b := 3
+c > b := true
+a == 1 := true
 ```
 
-This would log something like:
+You can also capture expressions that use commas inside parentheses
+(e.g. function calls), brackets, or braces (e.g. initializers). To
+properly capture expression that contains template parameters list
+(in other words, it contains commas between angle brackets), you need
+to enclose the expression inside parentheses:
+`CAPTURE( (std::pair<int, int>{1, 2}) );`
 
-<pre>"theAnswer := 42"</pre>
 
 ---