Check for unused sources removed

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-05-26 04:58:51

Hello,
I've just comitted a change which completely removed check for "unused 
sources". In short, this feature has caused too much trouble, and a couple of 
users reported that had to comment out the code anyway to avoid zillions of 
warnings.

The commit's log message, shown below, describes the specific problems we had.

- Volodya

Log message:
Remove check for 'unused sources'. The check causes bogus warnings in at least
a couple of cases.

1. On Windows, DLLs are never directly linked to, so they are considered
unused and cause a warning. There used to be special code in
exe-target-class and lib-target-class to supress that warning, but this
failed for unit-test, for example, since main target class for unit test
is not related with exe-target-class. And making yet another main target
class looks ugly.
2. A target specified via project-wide <source> or <library> property is
added to sources for all targets, and cause a warning when it's not used.
However, there are valid cases to ignore such sources. For example

obj a : a.cpp : <optimization>off ;

need to comsume any libraries.

It was not clear how to fix both problems. Further, the only case when I found
the warning to be usefull is when declaring new toolsets, and it that case it 
does not add much information compared to --debug-generators output. So, let's
just kill the feature for now.