Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/Squirrel/CMakeLists.txt

@@ -0,0 +1,69 @@
+# Create the Squirrel library
+add_library(Squirrel STATIC
+	include/sqconfig.h
+	include/sqstdaux.h
+	include/sqstdblob.h
+	include/sqstdmath.h
+	include/sqstdstring.h
+	include/sqstdsystem.h
+	include/squirrel.h
+	include/squirrelex.h
+	sqapi.cpp
+	sqapiex.cpp
+	sqarray.h
+	sqbaselib.cpp
+	sqclass.cpp sqclass.h
+	sqclosure.h
+	sqcompiler.cpp sqcompiler.h
+	sqdebug.cpp
+	sqfuncproto.h
+	sqfuncstate.cpp sqfuncstate.h
+	sqlexer.cpp sqlexer.h
+	sqmem.cpp
+	sqobject.cpp sqobject.h
+	sqopcodes.h
+	sqpcheader.h
+	sqstate.cpp sqstate.h
+	sqstring.h
+	sqtable.cpp sqtable.h
+	squserdata.h
+	squtils.h
+	sqvm.cpp sqvm.h
+	stdlib/sqstdaux.cpp
+	stdlib/sqstdblob.cpp
+	stdlib/sqstdblobimpl.h
+	stdlib/sqstdio.cpp
+	stdlib/sqstdmath.cpp
+	stdlib/sqstdrex.cpp
+	stdlib/sqstdstream.cpp
+	stdlib/sqstdstream.h
+	stdlib/sqstdstring.cpp
+	stdlib/sqstdsystem.cpp
+)
+# Determine if build mode
+if(CMAKE_BUILD_TYPE MATCHES "(Release)+")
+	target_compile_definitions(Squirrel PRIVATE NDEBUG=1)
+else()
+	target_compile_definitions(Squirrel PRIVATE _DEBUG=1)
+endif()
+# Make sure Squirrel knows this is 64 bit
+if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+    target_compile_definitions(Squirrel PUBLIC _SQ64)
+endif()
+# Set specific compiler options
+if (GCC OR MINGW)
+	target_compile_options(Squirrel PRIVATE -w
+		-fno-exceptions
+		-fno-rtti
+		-fno-strict-aliasing
+		-Wno-format
+		-Wno-unused-variable
+		-Wno-unused-but-set-variable
+	)
+endif()
+# Configure build options
+#target_compile_definitions(Squirrel PRIVATE GARBAGE_COLLECTOR=1)
+# Library includes
+target_include_directories(Squirrel PRIVATE ${CMAKE_CURRENT_LIST_DIR})
+target_include_directories(Squirrel PUBLIC ${CMAKE_CURRENT_LIST_DIR}/include)
+target_include_directories(Squirrel PRIVATE ${CMAKE_CURRENT_LIST_DIR}/stdlib)