libbb: introduce fputc_printable (from ed)

netstat: print control chars as ^C etc
vi: style fixlet

function                                             old     new   delta
fputc_printable                                        -     100    +100
unix_do_one                                          451     487     +36
printLines                                           258     190     -68
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 136/-68)            Total: 68 bytes

1 files changed, 2 insertions, 14 deletions

diff --git a/editors/ed.c b/editors/ed.c
index cceff0c40..a569788ad 100644
--- a/editors/ed.c
+++ b/editors/ed.c
@@ -847,20 +847,8 @@ static int printLines(int num1, int num2, int expandFlag)
                         count--;
 
                 while (count-- > 0) {
-                        ch = *cp++;
-                        if (ch & 0x80) {
-                                fputs("M-", stdout);
-                                ch &= 0x7f;
-                        }
-                        if (ch < ' ') {
-                                bb_putchar('^');
-                                ch += '@';
-                        }
-                        if (ch == 0x7f) {
-                                bb_putchar('^');
-                                ch = '?';
-                        }
-                        bb_putchar(ch);
+                        ch = (unsigned char) *cp++;
+                        fputc_printable(ch | PRINTABLE_META, stdout);
                 }
 
                 fputs("$\n", stdout);