main : don't print special tokens with --grammar (#6923)

* main : don't print special tokens with --grammar

The CLI interface was recently changed to print special control tokens
like the </s> stop message one. This token shouldn't be printed if the
grammar flag was passed, unless the grammar specifies it, because that
breaks shell-scriptability.

* main: use seperate stream for control characters

* main: use dprintf and add --ctrl-token-no-out and --ctrl-token-fd-out

* main: dprintf isn't part of the IEEE POSIX standard. Just use write().

* main: remove --ctrl-token-fd-out in favor for fcntl() based detection

* common.cpp: accidentally removed --interactive-first

* main: only merge stdout and control token if not in conversation or grammar mode

* main: rejig control token descriptor handling

* main: must check pipe status on very top of program

* main: renamed --no-special from  --ctrl-token-no-out and other refactoring

* main: refactor ctrl_token_no_out --> no_special

* llama: rename llama_token_is_control_token() to llama_token_is_control()

* main: remove special token file descriptor feature (#5)

---------

Co-authored-by: Brian <mofosyne@gmail.com>

llama.h

@@ -823,6 +823,9 @@ extern "C" {
     // Check if the token is supposed to end generation (end-of-generation, eg. EOS, EOT, etc.)
     LLAMA_API bool llama_token_is_eog(const struct llama_model * model, llama_token token);
 
+    // Identify if Token Id is a control token or a render-able token
+    LLAMA_API bool llama_token_is_control(const struct llama_model * model, llama_token token);
+
     // Special tokens
     LLAMA_API llama_token llama_token_bos(const struct llama_model * model); // beginning-of-sentence
     LLAMA_API llama_token llama_token_eos(const struct llama_model * model); // end-of-sentence