Implement avrdude_message2() from main.c

This is eventually to be replaced by a Python callback.
Right now, use what main.c is using.

src/libavrdude.i

@@ -25,9 +25,109 @@ int avrdude_message(int msglvl, const char *format, ...)
     return rc;
 }
 
-int avrdude_message2(FILE *fp, int lno, const char *file, const char *func, int msgmode, int msglvl, const char *format, ...) {
-  printf("avrdude_message2() called\n");
-  return 0;
+
+// This is the version from main.c
+// Should be handled by something overridable from Python
+int avrdude_message2(FILE *fp, int lno, const char *file,
+                     const char *func, int msgmode, int msglvl,
+                     const char *format, ...)
+{
+    int rc = 0;
+    va_list ap;
+
+    static struct {             // Memorise whether last print ended at beginning of line
+      FILE *fp;
+      int bol;                  // Are we at the beginning of a line for this fp stream?
+    } bols[5+1];                // Cater for up to 5 different FILE pointers plus one catch-all
+
+    size_t bi = 0;              // bi is index to bols[] array
+    for(bi=0; bi < sizeof bols/sizeof*bols -1; bi++) { // Note the -1, so bi is valid after loop
+      if(!bols[bi].fp) {        // First free space
+        bols[bi].fp = fp;       // Insert fp in first free space
+        bols[bi].bol = 1;       // Assume beginning of line on first use
+      }
+      if(bols[bi].fp == fp)
+        break;
+    }
+
+    if(msglvl <= MSG_ERROR)     // Serious error? Free progress bars (if any)
+      report_progress(1, -1, NULL);
+
+    if(msgmode & MSG2_FLUSH) {
+        fflush(stdout);
+        fflush(stderr);
+    }
+
+    // Reduce effective verbosity level by number of -q above one when printing to stderr
+    if ((quell_progress < 2 || fp != stderr? verbose: verbose+1-quell_progress) >= msglvl) {
+        if(msgmode & MSG2_PROGNAME) {
+          if(!bols[bi].bol)
+            fprintf(fp, "\n");
+          fprintf(fp, "%s", progname);
+          if(verbose >= MSG_NOTICE && (msgmode & MSG2_FUNCTION))
+            fprintf(fp, " %s()", func);
+          if(verbose >= MSG_DEBUG && (msgmode & MSG2_FILELINE)) {
+            const char *pr = strrchr(file, '/'); // Only print basename
+#if defined (WIN32)
+            if(!pr)
+              pr =  strrchr(file, '\\');
+#endif
+            pr = pr? pr+1: file;
+            fprintf(fp, " [%s:%d]", pr, lno);
+          }
+          if(msgmode & MSG2_TYPE)
+            fprintf(fp, " level %d", msglvl);
+          fprintf(fp, ": ");
+          bols[bi].bol = 0;
+        } else if(msgmode & MSG2_INDENT1) {
+          fprintf(fp, "%*s", (int) strlen(progname)+1, "");
+          bols[bi].bol = 0;
+        } else if(msgmode & MSG2_INDENT2) {
+          fprintf(fp, "%*s", (int) strlen(progname)+2, "");
+          bols[bi].bol = 0;
+        }
+
+        // Vertical tab at start of format string is a conditional new line
+        if(*format == '\v') {
+          format++;
+          if(!bols[bi].bol) {
+            fprintf(fp, "\n");
+            bols[bi].bol = 1;
+          }
+        }
+
+        // Figure out whether this print will leave us at beginning of line
+
+        // Determine required size first
+        va_start(ap, format);
+        rc = vsnprintf(NULL, 0, format, ap);
+        va_end(ap);
+
+        if(rc < 0)              // Some errror?
+          return 0;
+
+        rc++;                   // Accommodate terminating nul
+        char *p = cfg_malloc(__func__, rc);
+        va_start(ap, format);
+        rc = vsnprintf(p, rc, format, ap);
+        va_end(ap);
+
+        if(rc < 0) {
+          free(p);
+          return 0;
+        }
+
+        if(*p) {
+          fprintf(fp, "%s", p); // Finally: print!
+          bols[bi].bol = p[strlen(p)-1] == '\n';
+        }
+        free(p);
+    }
+
+    if(msgmode & MSG2_FLUSH)
+        fflush(fp);
+
+    return rc;
 }
 
 PROGRAMMER *cast_programmer(LNODEID p) {