compiler options in 'using'

[ghost]

Now, one can do:

using gcc : : <compileflags>foo <linkflags>bar ;

This confuses the user in two waits.

1. It's not possible to specify arbitrary features there, and unrecognized features

are ignored.

2. The <compileflags> is not a valid feature, so using it in Jamfiles does not work.

The root of the problem is names used in 'using' has no relation to features at all, but have the same syntax.