Infrastructure for modularizing protocol analyzers.

There's now a new directory "src/protocols/", and the plan is for each
protocol analyzer to eventually have its own subdirectory in there
that contains everything it defines (C++/pac/bif). The infrastructure
to make that happen is in place, and two analyzers have been
converted to the new model, HTTP and SSL; there's no further
HTTP/SSL-specific code anywhere else in the core anymore (I believe :-)

Further changes:

    - -N lists available plugins, -NN lists more details on what these
      plugins provide (analyzers, bif elements). (The latter does not
      work for analyzers that haven't been converted yet).

    - *.bif.bro files now go into scripts/base/bif/; and
      scripts/base/bif/plugins/ for bif files provided by plugins.

    - I've factored out the bifcl/binpac CMake magic from
      src/CMakeLists.txt to cmake/{BifCl,Binpac}

    - There's a new cmake/BroPlugin that contains magic to allow
      plugins to have a simple CMakeLists.txt. The hope is that
      eventually the same CMakeLists.txt can be used for compiling a
      plugin either statically or dynamically.

    - bifcl has a new option -c that changes the code it generates so
      that it can be used with a plugin.

TODOs:
    - "make install" is probably broken.
    - Broxygen is probably broken for plugin-defined events.
    - event groups are broken (do we want to keep them?)

src/plugin/Macros.h

@@ -0,0 +1,42 @@
+
+#ifndef PLUGIN_MACROS_H
+#define PLUGIN_MACROS_H
+
+#include "analyzer/PluginComponent.h"
+
+#define BRO_PLUGIN_VERSION_BUILTIN -1
+#define BRO_PLUGIN_API_VERSION      1
+
+#define _BRO_PLUGIN_VERSION_DEFAULT -1
+
+#define BRO_PLUGIN_BEGIN(_name)					\
+	namespace plugin { namespace _name {			\
+		class Plugin : public plugin::Plugin {		\
+		protected:					\
+			void Init()				\
+			{					\
+			plugin::Description _desc;		\
+			_desc.name = #_name;			\
+			_desc.version = _BRO_PLUGIN_VERSION_DEFAULT;	\
+			_desc.api_version = BRO_PLUGIN_API_VERSION;
+
+#define BRO_PLUGIN_END				\
+			SetDescription(_desc);	\
+			}			\
+		};				\
+						\
+	static Plugin __plugin;			\
+	} }
+
+#define BRO_PLUGIN_DESCRIPTION _desc.description
+#define BRO_PLUGIN_URL         _desc.url
+#define BRO_PLUGIN_VERSION     _desc.version
+
+#define BRO_PLUGIN_BIF_FILE(file)			\
+		std::list<std::pair<std::string, int> >  __bif_##file##_init();	\
+		AddBifInitFunction(&__bif_##file##_init);
+
+#define BRO_PLUGIN_ANALYZER(tag, factory, enabled, partial) \
+	AddComponent(new ::analyzer::PluginComponent(tag, factory, enabled, partial));
+
+#endif