ex_data part 2: doc fixes and CRYPTO_free_ex_index.

Add CRYPTO_free_ex_index (for shared libraries)
Unify and complete the documentation for all "ex_data" API's and objects.
Replace xxx_get_ex_new_index functions with a macro.
Added an exdata test.
Renamed the ex_data internal datatypes.

Reviewed-by: Matt Caswell <matt@openssl.org>

test/exdatatest.c

diff --git a/test/exdatatest.c b/test/exdatatest.c
new file mode 100644
index 0000000..96105bb
--- /dev/null
+++ b/test/exdatatest.c
@@ -0,0 +1,148 @@
+/* ====================================================================
+ * Copyright (c) 2015 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+#include <openssl/crypto.h>
+
+static long sargl;
+static void *sargp;
+static int sidx;
+
+static void exnew(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
+          int idx, long argl, void *argp)
+{
+    assert(idx == sidx);
+    assert(argl == sargl);
+    assert(argp == sargp);
+}
+
+static int exdup(CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from,
+          void *from_d, int idx, long argl, void *argp)
+{
+    assert(idx == sidx);
+    assert(argl == sargl);
+    assert(argp == sargp);
+    return 0;
+}
+
+static void exfree(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
+            int idx, long argl, void *argp)
+{
+    assert(idx == sidx);
+    assert(argl == sargl);
+    assert(argp == sargp);
+}
+
+typedef struct myobj_st {
+    CRYPTO_EX_DATA ex_data;
+    int id;
+} MYOBJ;
+
+static MYOBJ *MYOBJ_new()
+{
+    static int count = 0;
+    MYOBJ *obj = OPENSSL_malloc(sizeof(*obj));
+    int st;
+
+    obj->id = ++count;
+    st = CRYPTO_new_ex_data(CRYPTO_EX_INDEX_APP, obj, &obj->ex_data);
+    assert(st != 0);
+    return obj;
+}
+
+static void MYOBJ_sethello(MYOBJ *obj, char *cp)
+{
+    int st;
+
+    st = CRYPTO_set_ex_data(&obj->ex_data, sidx, cp);
+    assert(st != 0);
+}
+
+static char *MYOBJ_gethello(MYOBJ *obj)
+{
+    return CRYPTO_get_ex_data(&obj->ex_data, sidx);
+}
+
+static void MYOBJ_free(MYOBJ *obj)
+{
+    CRYPTO_free_ex_data(CRYPTO_EX_INDEX_APP, obj, &obj->ex_data);
+    OPENSSL_free(obj);
+}
+
+int main()
+{
+    MYOBJ *t1, *t2;
+    const char *cp;
+    char *p;
+
+    p = strdup("hello world");
+    sargl = 21;
+    sargp = malloc(1);
+    sidx = CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_APP, sargl, sargp,
+                                   exnew, exdup, exfree);
+    t1 = MYOBJ_new();
+    t2 = MYOBJ_new();
+    MYOBJ_sethello(t1, p);
+    cp = MYOBJ_gethello(t1);
+    assert(cp == p);
+    cp = MYOBJ_gethello(t2);
+    assert(cp == NULL);
+    MYOBJ_free(t1);
+    MYOBJ_free(t2);
+    free(sargp);
+    free(p);
+    return 0;
+}