LinuxProcess: print default buffer in ascii

`RichString_appendWide()` is more expensive than
`RichString_appendAscii()` due to the calls to `mbstowcs(3)` and
`iswprint(3)`.

Use the latter to print the process field buffer by default.

For the following fields this theoretically can corrupt the output:
  - SECATTR
  - CGROUP
  - CTID

linux/LinuxProcess.c

@@ -744,7 +744,7 @@ static void LinuxProcess_writeField(const Process* this, RichString* str, Proces
       Process_writeField(this, str, field);
       return;
    }
-   RichString_appendWide(str, attr, buffer);
+   RichString_appendAscii(str, attr, buffer);
 }
 
 static double adjustNaN(double num) {