Add possibility to build Firebird using embedded library.

Add SOCI_FIREBIRD_EMBEDDED option which can be set to ON to link with
libfbembed instead of libfbclient.

Also slightly update the Firebird backend documentation, it does work with 2.5
and not only the ancient 1.5 Firebird version.

CHANGES

@@ -1,5 +1,11 @@
 This file contains the history of changes in the SOCI library.
 
+---
+Version 4.0.0 differs from 3.2.x in the following ways:
+
+- Firebird
+-- Add SOCI_FIREBIRD_EMBEDDED option to allow building with embedded library.
+
 ---
 Version 3.2.2 differs from 3.2.1 in the following ways:
 

cmake/dependencies/Firebird.cmake

@@ -1,3 +1,6 @@
+option(SOCI_FIREBIRD_EMBEDDED "Use embedded library in Firebird backend" OFF)
+boost_report_value(SOCI_FIREBIRD_EMBEDDED)
+
 set(Firebird_FIND_QUIETLY TRUE)
 
 find_package(Firebird)

cmake/modules/FindFirebird.cmake

@@ -14,10 +14,15 @@ find_path(FIREBIRD_INCLUDE_DIR ibase.h
   $ENV{ProgramFiles}/Firebird/*/include
 )
 
+if(SOCI_FIREBIRD_EMBEDDED)
+  set(FIREBIRD_LIB_NAMES fbembed)
+else()
+  set(FIREBIRD_LIB_NAMES fbclient fbclient_ms)
+endif()
+
 find_library(FIREBIRD_LIBRARIES
   NAMES
-    fbclient
-    fbclient_ms
+    ${FIREBIRD_LIB_NAMES}
   PATHS
     /usr/lib
     $ENV{ProgramFiles}/Firebird/*/lib

docs/backends/firebird.html

@@ -42,8 +42,10 @@
 <h3 id="prerequisites">Prerequisites</h3>
 <h4 id="versions">Supported Versions</h4>
 
-<p>The SOCI Firebird backend is currently supported for use with Firebird 1.5.<br />
-Other versions of Firebird may work as well, but they have not been tested by the SOCI team.</p>
+<p>The SOCI Firebird backend supports versions of Firebird from 1.5 to 2.5 and
+can be used with either the client-server or embedded Firebird libraries. The
+former is the default, to select the latter set <tt>SOCI_FIREBIRD_EMBEDDED</tt>
+CMake option to <tt>ON</tt> value when building.</p>
 
 <h4 id="tested">Tested Platforms</h4>
 
@@ -53,6 +55,7 @@ Other versions of Firebird may work as well, but they have not been tested by th
 <tr><td>1.5.2.4731</td><td>SunOS 5.10</td><td>g++ 3.4.3</td></tr>
 <tr><td>1.5.2.4731</td><td>Windows XP</td><td>Visual C++ 8.0</td></tr>
 <tr><td>1.5.3.4870</td><td>Windows XP</td><td>Visual C++ 8.0 Professional</td></tr>
+<tr><td>2.5.2.26540</td><td>Debian GNU/Linux 7</td><td>g++ 4.7.2</td></tr>
 </tbody>
 </table>