special case of properties that starts with two minus letters. fix #56

Author: Horcrux7

src/com/inet/lib/less/LessParser.java

@@ -1334,7 +1334,7 @@ private static boolean isIdentifier( StringBuilder builder ) {
                         ch = builder.charAt( i++ );
                         continue FIRST;
                     }
-                    return false;
+                    return true; // special case of properties that starts with two minus letters. see https://developer.mozilla.org/de/docs/Web/CSS/var
                 case 'U':
                     if( builder.length() > 1 && builder.charAt( 1 ) == '+' ) {
                         //unicode-range

test/com/inet/lib/less/samples/general/minus.css

@@ -26,3 +26,9 @@
   calcCompact: calc(100%-98px);
   calcVariable: calc(90% -10px);
 }
+:root {
+  --main-bg-color: pink;
+}
+body {
+  background-color: var(--main-bg-color);
+}

test/com/inet/lib/less/samples/general/minus.less

@@ -29,4 +29,10 @@
   @a : 90%;
   @b : 10px;
   calcVariable: calc(@a -@b);
+}
+:root {
+  --main-bg-color: pink;
+}
+body {
+  background-color: var(--main-bg-color);
 }