* new/gcc.jam (init): New rule. Allows to specify alternative
gcc versions.
* new/toolset.jam
(using): New rule.
(set-target-variables): Bufgix. I was making indirect call
via variable with multiple values.
* new/build-request.jam
(looks-like-implicit-value): New rule.
(from-command-line): Use the above.
(convert-command-line-element): Don't validate
elements with dashes (this probably must be fixed).
[SVN r16468]