Bump antlr4-maven-plugin to 4.8-1 and adapt poliqarp-lexer syntax

Closes #74

Change-Id: I7e21879e866cc11a2a5553c828d118df38698421
diff --git a/pom.xml b/pom.xml
index e4cdd1a..cde601d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -64,7 +64,7 @@
 		<dependency>
 			<groupId>org.antlr</groupId>
 			<artifactId>antlr4-maven-plugin</artifactId>
-			<version>4.2</version>
+			<version>4.8-1</version>
 		</dependency>
 		<dependency>
 			<groupId>org.antlr</groupId>