[format] replace fputc calls with emit_sanitized_char

TODO.org

@@ -2,7 +2,6 @@ Writan:
  - Image support.
  - Additional error handling in the formatter.
  - Remove extraneous <p> tags in output.
- - Swap fputc for emit_sanitized_char everywhere.
 
 Pages:
  - Add a category theory page (more general, math).

format.c

@@ -69,7 +69,7 @@ emit_heading(FILE *input, FILE *output)
 
     char c;
     while ((c = fgetc(input)) != '\n')
-        fputc(c, output);
+        emit_sanitized_char(c, output);
 
     fprintf(output, "</h%d>", level);
 
@@ -226,7 +226,7 @@ emit_code_block(FILE *input, FILE *output)
     while ((c = fgetc(input)) != ']') {
         if (c == EOF)
             die("Unexpected EOF while converting code block.");
-        fputc(c, output);
+        emit_sanitized_char(c, output);
     }
 
     fprintf(output, "</pre>");
@@ -264,7 +264,7 @@ format(FILE *input, FILE *output)
 
     while ((c = fgetc(input)) != EOF) {
         if (c == '\\') { /* escaped character */
-            fputc(fgetc(input), output);
+            emit_sanitized_char(fgetc(input), output);
         }
         else if (c == '*' && lastc == '\n') { /* heading */
             emit_heading(input, output);

resources/writan-example.txt

@@ -22,3 +22,6 @@ Underneath is a code block.
 (define (frob x)
   (frobnicate x))
 ]
+
+> Some profound text someone said once. This is a blockquote. It can occupy
+> multiple lines.