- Fix build with enabled UPNP

- Switch to opt_CMAKE_BOOL

PR:		211977
Reported by:	arabesc@bk.ru

security/i2pd/files/patch-build_CMakeLists.txt

@@ -0,0 +1,11 @@
+--- build/CMakeLists.txt.orig	2016-08-12 15:07:00 UTC
++++ build/CMakeLists.txt
+@@ -357,7 +357,7 @@ if (WITH_BINARY)
+   endif ()
+ 
+   if (WITH_UPNP)
+-    target_link_libraries("${PROJECT_NAME}" "miniupnpc")
++	  target_link_libraries("${PROJECT_NAME}" "${MINIUPNPC_LIBRARY}")
+   endif ()
+ 
+   # FindBoost pulls pthread for thread which is broken for static linking at least on Ubuntu 15.04

security/i2pd/files/patch-build_cmake__modules_FindMiniUPnPc.cmake

@@ -0,0 +1,32 @@
+--- build/cmake_modules/FindMiniUPnPc.cmake.orig	2016-08-12 15:07:00 UTC
++++ build/cmake_modules/FindMiniUPnPc.cmake
+@@ -1,6 +1,6 @@
+ # - Find MINIUPNPC
+ 
+-if(MINIUPNPC_INCLUDE_DIR)
++if(MINIUPNPC_INCLUDE_DIR AND MINIUPNPC_LIBRARY)
+    set(MINIUPNPC_FOUND TRUE)
+ 
+ else()
+@@ -11,15 +11,18 @@ else()
+       $ENV{SystemDrive}
+       ${PROJECT_SOURCE_DIR}/../..
+       )
+-  
+-  if(MINIUPNPC_INCLUDE_DIR)
++
++  find_library(MINIUPNPC_LIBRARY miniupnpc)
++
++  if(MINIUPNPC_INCLUDE_DIR AND MINIUPNPC_LIBRARY)
+     set(MINIUPNPC_FOUND TRUE)
+     message(STATUS "Found MiniUPnP headers: ${MINIUPNPC_INCLUDE_DIR}")
++    message(STATUS "Found MiniUPnP library: ${MINIUPNPC_LIBRARY}")
+   else()
+     set(MINIUPNPC_FOUND FALSE)
+     message(STATUS "MiniUPnP not found.")
+   endif()
+ 
+-  mark_as_advanced(MINIUPNPC_INCLUDE_DIR)
++  mark_as_advanced(MINIUPNPC_INCLUDE_DIR MINIUPNPC_LIBRARY)
+   
+ endif()