libczmqcontainers: Add internal czmq lib

Problem: A bug in the czmq zhashx library would incorrectly
resize the hash.  See:

zeromq/czmq#2173

This would lead to significant performance issues as the hash would
take up far more memory than it should and iteration of the hash
would take an excess amount of time.

A solution to this problem was fixed in:

zeromq/czmq#2174

however the fix will not exist in most OS distributions for some
time.

Solution: We have copied in the zhashx implementation into a new
convenience library libczmqcontainers.  Code was copied from the
master branch at commit d4b1a1d884532e43e82b9055ceb0b84d1db5915c.
The library is copied in verbatim with only minor changes to headers
and header guards.

To avoid excess copying in from czmq, add a file czmq_internal.h
that copies in macros, headers, and typdefs needed by the localized
zhashx.

To avoid symbol collisions, add a file zhashx_map.h that will
convert all internal uses of "zhashx" to "fzhashx".

Add a generic czmq_containers.h, that callers can include to use
the internal zhashx over the shared library version.

All files containing copied in code maintain their czmq license
(Mozilla Public License Version 2.0).  All modifications to czmq
files and code were isolated to those files, no code from other
parts of flux-core were copied in. See:

https://www.mozilla.org/en-US/MPL/2.0/combining-mpl-and-gpl/

configure.ac

@@ -495,6 +495,7 @@ AC_CONFIG_FILES( \
   src/common/libterminus/Makefile \
   src/common/libhostlist/Makefile \
   src/common/librlist/Makefile \
+  src/common/libczmqcontainers/Makefile \
   src/bindings/Makefile \
   src/bindings/lua/Makefile \
   src/bindings/python/Makefile \

src/common/Makefile.am

@@ -21,7 +21,8 @@ SUBDIRS = \
 	libterminus \
 	libcontent \
 	libhostlist \
-	librlist
+	librlist \
+	libczmqcontainers
 
 AM_CFLAGS = $(WARNING_CFLAGS) $(CODE_COVERAGE_CFLAGS)
 AM_LDFLAGS = $(CODE_COVERAGE_LIBS)
@@ -42,6 +43,7 @@ libflux_internal_la_LIBADD = \
 	$(builddir)/libioencode/libioencode.la \
 	$(builddir)/librouter/librouter.la \
 	$(builddir)/libhostlist/libhostlist.la \
+	$(builddir)/libczmqcontainers/libczmqcontainers.la \
 	$(JANSSON_LIBS) \
 	$(ZMQ_LIBS) \
 	$(LIBUUID_LIBS) \

src/common/libczmqcontainers/Makefile.am

@@ -0,0 +1,22 @@
+AM_CFLAGS = \
+        $(WARNING_CFLAGS) \
+        $(CODE_COVERAGE_CFLAGS)
+
+AM_LDFLAGS = \
+        $(CODE_COVERAGE_LDFLAGS)
+
+AM_CPPFLAGS = \
+	-I$(top_srcdir) \
+	-I$(top_srcdir)/src/include \
+	$(ZMQ_CFLAGS)
+
+noinst_LTLIBRARIES = \
+	libczmqcontainers.la
+
+libczmqcontainers_la_SOURCES = \
+	czmq_containers.h \
+	czmq_internal.h \
+	zhashx.h \
+	zhashx.c \
+	zhash_primes.inc \
+	zhashx_map.h

src/common/libczmqcontainers/czmq_containers.h

@@ -0,0 +1,24 @@
+/************************************************************\
+ * Copyright 2021 Lawrence Livermore National Security, LLC
+ * (c.f. AUTHORS, NOTICE.LLNS, COPYING)
+ *
+ * This file is part of the Flux resource manager framework.
+ * For details, see https://github.com/flux-framework.
+ *
+ * SPDX-License-Identifier: LGPL-3.0
+\************************************************************/
+
+#ifndef _CZMQ_CONTAINERS_H
+#define _CZMQ_CONTAINERS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "zhashx.h"
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/common/libczmqcontainers/czmq_internal.h

@@ -0,0 +1,42 @@
+/*  =========================================================================
+    Copyright (c) the Contributors as noted in the AUTHORS file.
+    This file is part of CZMQ, the high-level C binding for 0MQ:
+    http://czmq.zeromq.org.
+
+    This Source Code Form is subject to the terms of the Mozilla Public
+    License, v. 2.0. If a copy of the MPL was not distributed with this
+    file, You can obtain one at http://mozilla.org/MPL/2.0/.
+    =========================================================================
+*/
+
+/* To avoid copying in an excess amount of code from czmq, the
+ * following have been manually cut and pasted in
+ */
+
+#ifndef __CZMQ_INTERNAL__
+#define __CZMQ_INTERNAL__
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <stdlib.h>
+
+#ifdef NDEBUG
+  #undef NDEBUG
+  #include <assert.h>
+  #define NDEBUG
+#else
+  #include <assert.h>
+#endif
+
+#define freen(x) do {free(x); x = NULL;} while(0)
+
+#ifndef CZMQ_EXPORT
+#define CZMQ_EXPORT
+#endif
+
+typedef struct _zhashx_t fzhashx_t;
+
+#endif
+