Add scripting (tengo) support for every incoming message (#731)

TengoModifyMessage allows you to specify the location of a tengo (https://github.com/d5/tengo/) script.
This script will receive every incoming message and can be used to modify the Username and the Text of that message.
The script will have the following global variables:
to modify: msgUsername and msgText
to read: msgChannel and msgAccount

The script is reloaded on every message, so you can modify the script on the fly.

Example script can be found in https://github.com/42wim/matterbridge/tree/master/gateway/bench.tengo
and https://github.com/42wim/matterbridge/tree/master/contrib/example.tengo

The example below will check if the text contains blah and if so, it'll replace the text and the username of that message.
text := import("text")
if text.re_match("blah",msgText) {
    msgText="replaced by this"
    msgUsername="fakeuser"
}

More information about tengo on: https://github.com/d5/tengo/blob/master/docs/tutorial.md and
https://github.com/d5/tengo/blob/master/docs/stdlib.md

vendor/github.com/d5/tengo/compiler/compiler_logical.go

@@ -0,0 +1,30 @@
+package compiler
+
+import (
+	"github.com/d5/tengo/compiler/ast"
+	"github.com/d5/tengo/compiler/token"
+)
+
+func (c *Compiler) compileLogical(node *ast.BinaryExpr) error {
+	// left side term
+	if err := c.Compile(node.LHS); err != nil {
+		return err
+	}
+
+	// jump position
+	var jumpPos int
+	if node.Token == token.LAnd {
+		jumpPos = c.emit(node, OpAndJump, 0)
+	} else {
+		jumpPos = c.emit(node, OpOrJump, 0)
+	}
+
+	// right side term
+	if err := c.Compile(node.RHS); err != nil {
+		return err
+	}
+
+	c.changeOperand(jumpPos, len(c.currentInstructions()))
+
+	return nil
+}