Report OpenSSL build date too.

Adjust `-d -bV` output for OpenSSL to include library build date.

Some OS packagers have backported heartbleed security fixes without
changing anything in the reported version number.  The closest we can
get to a reassuring sign for administrators is to report the OpenSSL
library build date, as picked by the library which Exim is using at run
time.

```
Library version: OpenSSL: Compile: OpenSSL 1.0.1g 7 Apr 2014
                          Runtime: OpenSSL 1.0.1g 7 Apr 2014
                                 : built on: Mon Apr  7 15:08:30 PDT 2014
```

For comparison, the version information for OpenSSL on Ubuntu (where
Exim is by default built with GnuTLS, but this provides for context for
comparison):

```
$ openssl version -v -b
OpenSSL 1.0.1 14 Mar 2012
built on: Mon Apr  7 20:33:29 UTC 2014
```

GnuTLS: the closest I can find to a runtime value is the call we are
already making; if an OS vendor patches GnuTLS without changing the
version which would be returned by `gnutls_check_version(NULL)` then the
sysadmin is SOL and will have to explore library linkages more
carefully.

1 files changed, 11 insertions, 2 deletions

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index a64f85dea..b7b2f8847 100644
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -1923,6 +1923,11 @@ one version of OpenSSL but the run-time linker picks up another version,
 it can result in serious failures, including crashing with a SIGSEGV.  So
 report the version found by the compiler and the run-time version.
 
+Note: some OS vendors backport security fixes without changing the version
+number/string, and the version date remains unchanged.  The _build_ date
+will change, so we can more usefully assist with version diagnosis by also
+reporting the build date.
+
 Arguments:   a FILE* to print the results to
 Returns:     nothing
 */
@@ -1931,9 +1936,13 @@ void
 tls_version_report(FILE *f)
 {
 fprintf(f, "Library version: OpenSSL: Compile: %s\n"
-           "                          Runtime: %s\n",
+           "                          Runtime: %s\n"
+           "                                 : %s\n",
            OPENSSL_VERSION_TEXT,
-           SSLeay_version(SSLEAY_VERSION));
+           SSLeay_version(SSLEAY_VERSION),
+           SSLeay_version(SSLEAY_BUILT_ON));
+/* third line is 38 characters for the %s and the line is 73 chars long;
+the OpenSSL output includes a "built on: " prefix already. */
 }