Add function declarations in atoe.c for Open XL

[Deigue]

Open XL on z/OS throws undeclared function errors when a function is used before it has been declared or defined. The changes here reorder the function definitions so that these errors are addressed.

i.e. The function definitions are moved above, so that their definitions are available before their respective usages.

/omr/util/a2e/atoe.c:1343:8: error: call to undeclared function 'atoe_vfprintf'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]                                                                                                              
 1343 |         len = atoe_vfprintf(file, ascii_chars, args);
      |               ^
      
omr/util/a2e/atoe.c:1362:8: error: call to undeclared function 'atoe_vfprintf'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
 1362 |         len = atoe_vfprintf(stdout, ascii_chars, args);
      |               ^
omr/util/a2e/atoe.c:1404:8: error: call to undeclared function 'atoe_vsprintf'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
 1404 |         len = atoe_vsprintf(buf, ascii_chars, args);
      |               ^

omr/util/a2e/atoe.c:1451:8: error: call to undeclared function 'atoe_vsprintf'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
 1451 |         len = atoe_vsprintf(buf, ascii_chars, args);
      |               ^

[Deigue]

@keithc-ca @babsingh Found a few new undeclared function errors with Open XL, when rebasing the latest changes from master, just needed some reordering of functions in atoe.c ... Tagging to get this noticed earlier.

[keithc-ca]

Rather than reordering, suggest just adding declarations for those functions which are referenced before they are defined (we already have some such declarations near line 161).

[Deigue]

Thanks, reverted the reordering, added the declarations and corrected the commit description/title accordingly.

[keithc-ca]

Suggest the parameters should have names or be improved:

int   atoe_fprintf(FILE *file, const char *fmt, ...);
int   atoe_vfprintf(FILE *file, const char *fmt, va_list args);
int   atoe_vsnprintf(char *buf, size_t buflen, const char *fmt, va_list args);
int   atoe_vsprintf(char *buf, const char *fmt, va_list args);