[RFA] ld.texinfo: clarify auto-import documentation

[Charles Wilson]

Given some recent confusion on the cygwin mailing list concerning 
auto-import, I figured it would be a good idea to expand this 
documentation slightly.

Short version: the recently fixed bug where ld silently created buggy 
code when auto-importing multiword variables (arrays, structs) also 
applies to OTHER multiword vars (long longs, etc).  The documentation 
implied that ONLY arrays and structs would trigger the "fix" error 
message;  these changes make it clear that several data types can give 
rise to that behavior.

Okay to apply?

--Chuck