Refector JSON parsing to use libjansson

The libjansson parser has better documentation
and better error reporting. The API is easier
to use resulting in less code required for
JSON parsing.

The __decomp decorator in front of most plugin
symbols has also been removed as this is
unnecessary for static symbols and variables.

configure.ac

@@ -65,6 +65,8 @@ AC_C_FLEXIBLE_ARRAY_MEMBER
 OVIS_PKGLIBDIR
 
 AC_LIB_HAVE_LINKFLAGS([jansson], [], [#include <jansson.h>])
+AS_IF([test "x$HAVE_LIBJANSSON" = xno],
+	[AC_MSG_ERROR([libjansson or jansson.h not found])])
 AM_CONDITIONAL([HAVE_LIBJANSSON], [test "x$HAVE_LIBJANSSON" = xyes])
 
 dnl change sharedstatedir default

ldms/src/decomp/as_is/Makefile.am

@@ -8,5 +8,5 @@ DECOMP_LIBADD = ../../core/libldms.la \
 		../../ldmsd/libldmsd_request.la
 
 libdecomp_as_is_la_SOURCES = decomp_as_is.c
-libdecomp_as_is_la_LIBADD  = $(DECOMP_LIBADD)
+libdecomp_as_is_la_LIBADD  = $(DECOMP_LIBADD) $(LTLIBJANSSON)
 pkglib_LTLIBRARIES += libdecomp_as_is.la