printf: add support for C23 'b' format, controlled by a flag.

A new label is added in the library named ~C23ORLATER. Its presence in the executable acts as a flag for enabling C23 library behavior, including the new 'b' format. The compiler will generate a reference to it when compiling a program in C23 mode, causing it to be linked in. This can then be detected in library code by including a soft (weak) reference to it, which will be non-zero if the flag is linked in (C23+) or zero if it is not (pre-C23).

cc.asm

@@ -16,6 +16,27 @@ CC       start                          dummy routine
 
          end
 
+****************************************************************
+*
+*  ~C23orLater - Flag indicating use of C23 or later standards
+*
+*  Notes:
+*        If a program is compiled in C23 mode (or later),
+*        ORCA/C will include a reference to ~C23orLater in its
+*        object code, causing this segment to be linked in.
+*        Library code should include only soft references to it.
+*        "lda #~C23orLater(soft reference)" will give 0 for
+*        pre-C23 modes, or nonzero for C23+, so library code
+*        can detect the language mode and behave accordingly.
+*
+****************************************************************
+*
+~C23Flag start
+         ds    1                        padding to ensure ~C23orLater ...
+~C23orLater entry
+         ds    1                        ... is not at start of a bank
+         end
+
 ****************************************************************
 *
 *  ~CopyBF - Copy a bit field

stdio.asm

@@ -4232,6 +4232,7 @@ lb1      clc                            restore the original argp+4
 *  ~Format_x - format a hexadecimal number (lowercase output)
 *  ~Format_X - format a hexadecimal number (uppercase output)
 *  ~Format_p - format a pointer
+*  ~Format_b_C23 - format a binary number (lowercase prefix, if any)
 *  ~Format_B - format a binary number (uppercase prefix, if any)
 *
 *  Inputs:
@@ -4253,6 +4254,10 @@ argp     equ   7                        argument pointer
          lda   #3                       use 3 bits per output character
          bra   cn0a
 
+~Format_b_C23 entry
+         ldx   #$20*256                 set the "or" value for case of '0b'
+         bra   bn0
+
 ~Format_B entry
          ldx   #0
 bn0      lda   #1                       use 1 bit per output character
@@ -4392,6 +4397,11 @@ argp     equ   7                        argument pointer
          bra   lb0
 
 ~Format_b entry
+         dc    i1'$A9'                  lda #~C23orLater (if linked in) or #0
+         dc    s2'~C23ORLATER'            (this must be on a separate line)
+         beq   ~Format_P                if doing C23 or later then
+         brl   ~Format_b_C23              use C23 version of 'b' format
+
 ~Format_P entry
          clc                            set flag for p-string