Fix:
$PAGE->context must be reset when calling validate_context
Improve:
Provide wrapper for calling an external function
The wrapper correctly checks the function parameters and return type against
the description of the external function, and stores the PAGE and COURSE global
state variables, restoring them before the function returns.
Fix: buggy unit tests.
These tests are expecting debugging from a bug that was fixed, and calling web
service functions with no user or session.
The benefit is that this becomes one test per external function instead of one
test testing them all - so more information is shown on failure and we get lots
more dots (we love dots!).
Optional params are not allowed as the top level value for external_function_parameters.
This is because stricter protocols (xmlrpc and soap) cannot handle optional parameters, only
optional properties in a structure.
API functions do not know if they are being called from a web page, or a
web-service. They need a single function to call to correctly apply
filters, strip tags etc that knows the correct way to do this based on
the way it was called (e.g. webservices allow parameters for skipping
filters etc).
So here we are fixing the default for the filter argument used in
external_format_text and adding a matching external_format_string.
Includes:
* constants refactoring
* reworked db table init
* support for $CFG->debug = -1
* functional DB tests
* fixed $DB->get_indexes() to not throw exceptions when table does not exist
* fix handling of user passwords in test db
* add debug info to exception messages
* removed unnecessary PHP debug errors from mathslib
* fixed @error suppression in get_string
* fixed PHPUnit error handler setup
* added timezone info to default install
