Battles: Support overriding line sections

Really this should probably be handled with `|` rather than with
a complicated system for guessing where to break messages... but
it's easier not to change these old systems.

Author: Zarel

play.pokemonshowdown.com/src/battle-text-parser.ts

@@ -385,6 +385,10 @@ export class BattleTextParser {
 	}
 
 	lineSection(args: Args, kwArgs: KWArgs) {
+		if (kwArgs.premajor) return 'preMajor';
+		if (kwArgs.postmajor) return 'postMajor';
+		if (kwArgs.major) return 'major';
+
 		const cmd = args[0];
 		switch (cmd) {
 		case 'done' : case 'turn':