Because of limitations in the C type system, we can't a strtok_len
that can work on both const string and non-const strings. The C
library solves this by taking a const char* and returning a char*
in functions like this (e.g., strchr), but that's not const-safe.
Solve it by introducing strtok_len_c, a version of strtok_len for
const strings.
This parses the subset of Xapian's boolean term quoting rules that are
used by make_boolean_term. This is provided as a generic string
utility, but will be used shortly in notmuch restore to parse and
optimize for ID queries.
This is now a generic boolean term quoting function. It performs
minimal quoting to produce user-friendly queries.
This could live in tag-util as well, but it is really nothing specific
to tags (although the conventions are specific to Xapian).
The API is changed from "caller-allocates" to "readline-like". The
scan for max tag length is pushed down into the quoting routine.
Furthermore, this now combines the term prefix with the quoted term;
arguably this is just as easy to do in the caller, but this will
nicely parallel the boolean term parsing function to be introduced
shortly.
This is an amalgamation of code written by David Bremner and myself.
This is to give a home to strtok_len. It's a bit silly to add a header
for one routine, but it needs to be shared between several compilation
units (or at least that's the most natural design).
