Basic standard graphics

[Adam D. Ruppe]

bearophile wrote:
> std.conv.text() may be better there (untested):

Cool! I never realized that function existed.

It might be a nice enhancement to add a ctext() that returns
the string zero-terminated and as a char* for use with C functions.

(Actually, I think C functions should take ubyte* instead of char*
because they aren't necessarily UTF-8 but most bindings don't do
this so char* might work better in practice. Or maybe inventing
a new typedef or struct just for C is the best.)

While toStringz does this, a helper function might make C
libraries just a little easier and safer to use.