Backed out changeset c52eeea62763

FFI: do not handle "const" return values specially It is unclear what this special handling was / is good for. However, if one wants something along these lines, one can always override `#fromExternalAddress:` and perform custom logic there.

FFI: do not define `CALLTYPE_FFI_UNIX64` on i686 machines ...since it is not defined there. This fixes compilation issue on i686 when using libffi (which is now default on all platforms)

Fix `Context >> argAndVarNames` in cases when debug info is not available

FFI: refactor creation of return value from FFI call-outs. To allow customized creation / initialization of ExternalAddress subclasses, FFI machinery now falls `SomeClass fromExternalAddress:` when FFI call-out is specified to return an instance of `SomeClass`. This way, user (sub)classes may override `#fromExternalAddress:` and perform custom logic.

FFI: properly convert signed/unsigned integer return values to smalltalk integers The code converting integer return value did not care properly for all integer types and for signedness, causing `int` return type to return (positive) 0xffffffff value instead of -1. This commit fixes the problem by properly defining return union members for all supported bitwidths and signedness and by proper type conversion using cast operator when passing narrower values to `__MKINT()` and `__MKUINT()`. However, the FFI code should be revisited and cleaned up anyway.

Add `CharacterArray >> findString:startingAt:caseSensitive:`

Add `StringCollection >> asCollectionOfWords` ...to make it somewhat polymorphic with String.

Fix `Class >> #validateSourceStream:` w.r.t. classes loaded from source Classes loaded from source have no binary checksum so checksum test would fail. Current code was a bit defensive, assuming the source stream is NOT valid if there's no valid binary checksum, causing `#validateSourceStream:` to fail for source-loaded classes. This commit fixes this by checking if it's really source-loaded (i.e., no method is compiled) and in such case, return `true`. This check will be removed later once this proves to work fine.

Merge