Added first shot at a development shell

Added development shell (d8) including readline support, counters and
completion.

[Christian Plesner Hansen, 2008-10-21 07:26:31]

I've updated this changelist.  Now the javascript code from within d8.cc is
factored out into d8.js and the natives infrastructure has been changed to allow
several generated natives files.

[Kasper Lund, 2008-10-21 08:26:56]

LGTM. I guess the next step is to start using d8 to run our tests instead of the
shell sample. Is there anything we could remove from the shell sample once d8 is
alive and kicking?

http://codereview.chromium.org/7519/diff/401/605
File src/d8.h (right):

http://codereview.chromium.org/7519/diff/401/605#newcode108
Line 108: }  // v8
Maybe add some more whitespace here. There's plenty in other parts of the the
file.

http://codereview.chromium.org/7519/diff/401/606
File src/d8.js (right):

http://codereview.chromium.org/7519/diff/401/606#newcode33
Line 33: for (var i = 0; i < str.length; i++) {
How about using substring and string equality check?

http://codereview.chromium.org/7519/diff/401/606#newcode42
Line 42: return undefined;
I don't trust undefined not to be overwritten by users. I would just use
'return' - or maybe 'return void 0'.

http://codereview.chromium.org/7519/diff/401/606#newcode54
Line 54: for (var i in parts) {
This looks weird. Do you really want all the keys (0, 1, ...) as strings? Why
not use a for (var i = 0; i < parts.length; i++)?

http://codereview.chromium.org/7519/diff/401/606#newcode63
Line 63: while (current !== undefined) {
I would use a typeof check against 'undefined' here.

http://codereview.chromium.org/7519/diff/401/606#newcode66
Line 66: for (var i in properties) {
Do you really want to use for-in here too?