configure: Separate pki from --disable-tools

While pki builds and runs just fine on Windows, this is not true for scepclient.

conf/Makefile.am

@@ -18,6 +18,7 @@ options = \
 	options/pool.opt \
 	options/starter.opt \
 	options/tnc.opt \
+	options/pki.opt \
 	options/tools.opt
 
 plugins = \

conf/options/pki.opt

@@ -0,0 +1,2 @@
+pki.load =
+	Plugins to load in ipsec pki tool.

conf/options/tools.opt

@@ -1,5 +1,2 @@
-pki.load =
-	Plugins to load in ipsec pki tool.
-
 scepclient.load =
 	Plugins to load in ipsec scepclient tool.