[PATCH v3 0/3] Structured Formatters

[craven at gmx.net]

Currently there is no easy way to add support for different structured
formatters (like JSON). For example, adding support for S-Expressions
would result in code duplication.

This patch series amends the situation by introducing structured
formatters, which allow different implementations of structures like
lists, maps, strings and numbers.

The new code in structured-output.h and structured-output.c can be used
instead of the current ad-hoc output in all parts of notmuch, a patch
for notmuch-search.c is included.

In a later patch, all other parts of notmuch should be adapted to the
structured formatters, and the creation of formatters should be
centralised (to make adding new formatters easier).