Add support for SGR 53, 55 overline

Specced in ECMA-48

src/common/InputHandler.ts

@@ -2551,6 +2551,12 @@ export class InputHandler extends Disposable implements IInputHandler {
       } else if (p === 38 || p === 48 || p === 58) {
         // fg color 256 and RGB
         i += this._extractColor(params, i, attr);
+      } else if (p === 53) {
+        // overline
+        attr.bg |= BgFlags.OVERLINE;
+      } else if (p === 55) {
+        // not overline
+        attr.bg &= ~BgFlags.OVERLINE;
       } else if (p === 59) {
         attr.extended = attr.extended.clone();
         attr.extended.underlineColor = -1;

src/common/Types.d.ts

@@ -165,6 +165,7 @@ export interface IAttributeData {
   isDim(): number;
   isStrikethrough(): number;
   isProtected(): number;
+  isOverline(): number;
 
   /**
    * The color mode of the foreground color which determines how to decode {@link getFgColor},

src/common/buffer/AttributeData.ts

@@ -47,6 +47,7 @@ export class AttributeData implements IAttributeData {
   public isDim(): number           { return this.bg & BgFlags.DIM; }
   public isStrikethrough(): number { return this.fg & FgFlags.STRIKETHROUGH; }
   public isProtected(): number     { return this.bg & BgFlags.PROTECTED; }
+  public isOverline(): number      { return this.bg & BgFlags.OVERLINE; }
 
   // color modes
   public getFgColorMode(): number { return this.fg & Attributes.CM_MASK; }

src/common/buffer/Constants.ts

@@ -128,7 +128,8 @@ export const enum BgFlags {
   ITALIC = 0x4000000,
   DIM = 0x8000000,
   HAS_EXTENDED = 0x10000000,
-  PROTECTED = 0x20000000
+  PROTECTED = 0x20000000,
+  OVERLINE = 0x40000000
 }
 
 export const enum ExtFlags {