Configure flags and universal variants

[Paul Guyot]

Hi all,

Trunk contains new code for configure flags and default universal  
variant code.

It would be great if this could be tested more and released as soon  
as possible:
- it would allow maintainers to work on universal variants
- it would allow us to simplify many portfiles by removing:
configure.env CFLAGS=-I${prefix}/include LDFLAGS=-L${prefix}/lib

Besides, trunk code produces -O2 binaries for autoconf-based ports,  
while any such port with the previous line is compiled -O0 with 1.4.0.

Paul