General GC optimizations (#3221)

- Enable recursive GC marking with a limited recursion count (this option is configurable)
- No need to decrease the reference count of the gray objects anymore
- Bound function object marking is seperated into a helper function

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

docs/01.CONFIGURATION.md

@@ -211,6 +211,17 @@ A value of 0 will use the default value.
 | CMake:  | `-DJERRY_GC_LIMIT=(int)`                     |
 | Python: | `--gc-limit=(int)`                           |
 
+### GC mark recursion limit
+
+This option can be used to adjust the maximum recursion depth during the GC mark phase. The provided value should be an integer, which represents the allowed number of recursive calls. Increasing the depth of the recursion reduces the time of GC cycles, however increases stack usage.
+A value of 0 will prevent any recursive GC calls.
+
+| Options |                                                   |
+|---------|---------------------------------------------------|
+| C:      | `-DJERRY_GC_MARK_LIMIT=(int)`                     |
+| CMake:  | `-DJERRY_GC_MARK_LIMIT=(int)`                     |
+| Python: | `--gc-mark-limit=(int)`                           |
+
 ### Stack limit
 
 This option can be used to cap the stack usage of the engine, and prevent stack overflows due to recursion. The provided value should be an integer, which represents the allowed stack usage in kilobytes.
@@ -296,7 +307,7 @@ These files can be directly compiled with an application using the JerryScript A
 For example with the following command:
 
 ```sh
-$ gcc -Wall -o demo_app demo_app.c gen_src/jerryscript.c gen_src/jerryscript-port-default.c jerryscript-libm.c -Igen_src/ 
+$ gcc -Wall -o demo_app demo_app.c gen_src/jerryscript.c gen_src/jerryscript-port-default.c jerryscript-libm.c -Igen_src/
 ```
 
 Please note that the headers must be available on the include path.