Adding an S-expression structured output printer.

This commit adds a structured output printer for Lisp
S-Expressions. Later commits will use this printer in notmuch search,
show and reply.

The structure is the same as json, but:
- arrays are written as lists: ("foo" "bar" "baaz" 1 2 3)
- maps are written as p-lists: (:key "value" :other-key "other-value")
- true is written as t
- false is written as nil
- null is written as nil

[ whitespace changes by db ]

1 files changed, 4 insertions, 0 deletions

diff --git a/sprinter.h b/sprinter.h
index 912a5262..59776a9c 100644
--- a/sprinter.h
+++ b/sprinter.h
@@ -70,4 +70,8 @@ sprinter_text_create (const void *ctx, FILE *stream);
 struct sprinter *
 sprinter_json_create (const void *ctx, FILE *stream);
 
+/* Create a new structure printer that emits S-Expressions. */
+struct sprinter *
+sprinter_sexp_create (const void *ctx, FILE *stream);
+
 #endif // NOTMUCH_SPRINTER_H