closes#291
This changes the error message "return value ignored" to "expression value is ignored".
This is because this error also applies to {1;}, which has no function calls.
Also fix ignored expression values in std and test.
This caught a bug in debug.readAllocBytes where an early Eof error would have been missed.
See #219.
* add `setFnTest`, `setFnVisible`, `setFnStaticEval`,
`setFnNoInline` builtin functions to replace previous
directive functionality
* add `coldcc` and `nakedcc` as keywords which can be used as part
of a function prototype.
* `setDebugSafety` builtin can be used to set debug safety features
at a per block scope level.
* closes#169