Slightly clean up is_callable implementation

And adjust an error message to line up with the error message
used for $callable() in zend_execute.c.

Allow array_diff() and array_intersect() with single array argument

Both of these functions are well-defined when used with a single
array argument -- rejecting this case was an artifici

Allow array_diff() and array_intersect() with single array argument

Both of these functions are well-defined when used with a single
array argument -- rejecting this case was an artificial limitation.
This is not useful when called with explicit arguments, but removes
edge-cases when used with argument unpacking:

// OK even if $excludes is empty.
array_diff($array, ...$excludes);

// OK even if $arrays contains a single array only.
array_intersect(...$arrays);

This matches the behavior of functions like array_merge() and
array_push(), which also allow calls with no array or a single
array respectively.

Closes GH-6097.

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Improve error messages mentioning parameters instead of arguments

Closes GH-5999

Remove unnecessary PHPDoc-alike blocks from tests

Closes GH-5759

Change argument error message format

Closes GH-5211

Make type error messages more consistent

Closes GH-5092

Clean DONE tags from tests

Remove most of the `===DONE===` tags and its variations.
Keep `===DONE===` if the test output otherwise becomes empty.

Closes GH-4872.

Convert some warnings to TypeErrors in array functions

This is manual type and argument number checking code that was not
covered by the zpp move to TypeErrors.

Adjust tests for zpp TypeError change

Trim trailing whitespace in *.phpt

Array tests: checked on PHP 5.2.6, 5.3 and 6.0 (Windows, Linux and Linux 64 bit).

New testcases for array_diff_uassoc() function