Implement a new `count(f)` method on the Sequence class that accepts a predicate function and returns the number of elements for which the predicate evaluates to true. The implementation iterates over the sequence, calling `f.call(element)` on each element and incrementing a counter when the result is truthy.
Also update the documentation for both Sequence and List classes: add full documentation for the new `count(predicate)` method on Sequence, and change the terminology in List docs from "items" to "elements" for consistency. Add three test files covering the basic predicate behavior, non-boolean return values from the predicate, and the error case when a non-function argument is passed.
Change the `capacity` and `count` fields in `ObjList` from `int` to `uint32_t` to match the
types used in `ObjMap`, ensuring consistency between the two structures. Update all loop
variables and index calculations in `wren_core.c` and `wren_value.c` that interact with
these fields to use `uint32_t` instead of `int`, and remove the now-unnecessary negative
bounds check in `list_iterate` since unsigned types cannot be negative.
Enable the -Wextra compiler flag in the wren.mk build configuration, which was previously commented out with a TODO. To handle the new unused parameter warnings triggered by -Wextra (particularly for WrenVM* vm parameters in several functions), add -Wno-unused-parameter to suppress them. Also fix a declaration ordering issue in wren_vm.c where the 'static' keyword was placed after the return type in loadIntoCore, moving it to the correct position before the type specifier.
The guard checks if the VM pointer is NULL or if its methodNames count is zero,
which serves as a heuristic to detect an already-freed VM instance. This prevents
a segmentation fault or memory corruption when wrenFreeVM is called multiple times
on the same VM object.
