* src/util/json.c (virJSONValueFree): Free the "value" pointer, too.

* src/util/json.c, src/util/json.h: Declare returned strings
  to be const
* src/qemu/qemu_monitor.c: Wire up JSON mode for qemuMonitorGetPtyPaths
* src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h: Fix
  const correctness. Add missing error message in the function
  qemuMonitorJSONGetAllPCIAddresses. Add implementation of the
  qemuMonitorGetPtyPaths function calling 'query-chardev'.

Alter the offending variable names to fix this.

configure:     yajl: no
CC     libvirt_util_la-json.lo
util/json.c:32:27: error: yajl/yajl_gen.h: No such file or directory
util/json.c:33:29: error: yajl/yajl_parse.h: No such file or directory

* src/util/json.c: remove the includes if yajl not configured in

* src/util/json.c: Fix ReprotError typo when YAJL is not available

This introduces simple API for handling JSON data. There is
an internal data structure 'virJSONValuePtr' which stores a
arbitrary nested JSON value (number, string, array, object,
nul, etc).  There are APIs for constructing/querying objects
and APIs for parsing/formatting string formatted JSON data.

This uses the YAJL library for parsing/formatting from

 http://lloyd.github.com/yajl/

* src/util/json.h, src/util/json.c: Data structures and APIs
  for representing JSON data, and parsing/formatting it
* configure.in: Add check for yajl library
* libvirt.spec.in: Add build requires for yajl
* src/Makefile.am: Add json.c/h
* src/libvirt_private.syms: Export JSON symbols to drivers