Log assert messages

Now, assert messages as visible in the trace output
as well as the line number of condition that failed.
Rename CCScriptSupport::executeAssert -> CCScriptSupport::handleAssert

Also remove the first "cond" argument, since it is always false.
Merge pull request #2391 from sbc100/log_asserts

fixed #2152: Logging assert messages to the console and renaming CCScriptSupport::executeAssert to CCScriptSupport::handleAssert.
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