csharp: add support for binary literals and _ as separator

Note that proper `_` usage is not enforced; this matches vscode behavior.

src/csharp.ts

@@ -102,9 +102,10 @@ export var language = <ILanguage> {
 			[/\$"/, { token: 'string.quote', next: '@interpolatedstring' } ],
 
 			// numbers
-			[/\d*\.\d+([eE][\-+]?\d+)?[fFdD]?/, 'number.float'],
-			[/0[xX][0-9a-fA-F]+/, 'number.hex'],
-			[/\d+/, 'number'],
+			[/[0-9_]*\.[0-9_]+([eE][\-+]?\d+)?[fFdD]?/, 'number.float'],
+			[/0[xX][0-9a-fA-F_]+/, 'number.hex'],
+			[/0[bB][01_]+/, 'number.hex'], // binary: use same theme style as hex
+			[/[0-9_]+/, 'number'],
 
 			// delimiter: after number because of .\d floats
 			[/[;,.]/, 'delimiter'],

test/csharp.test.ts

@@ -525,6 +525,12 @@ testTokenization('csharp', [
 		{ startIndex: 0, type: 'number.cs' }
 	]}],
 
+	[{
+	line: '123_456',
+	tokens: [
+		{ startIndex: 0, type: 'number.cs' }
+	]}],
+
 	[{
 	line: '0x',
 	tokens: [
@@ -532,18 +538,49 @@ testTokenization('csharp', [
 		{ startIndex: 1, type: 'identifier.cs' }
 	]}],
 
+	[{
+	line: '0b',
+	tokens: [
+		{ startIndex: 0, type: 'number.cs' },
+		{ startIndex: 1, type: 'identifier.cs' }
+	]}],
+
 	[{
 	line: '0x123',
 	tokens: [
 		{ startIndex: 0, type: 'number.hex.cs' }
 	]}],
 
+	[{
+	line: '0x123_456',
+	tokens: [
+		{ startIndex: 0, type: 'number.hex.cs' }
+	]}],
+
+	[{
+	line: '0b101',
+	tokens: [
+		{ startIndex: 0, type: 'number.hex.cs' }
+	]}],
+
+	[{
+	line: '0b1010_0001',
+	tokens: [
+		{ startIndex: 0, type: 'number.hex.cs' }
+	]}],
+
 	[{
 	line: '23.5',
 	tokens: [
 		{ startIndex: 0, type: 'number.float.cs' }
 	]}],
 
+	[{
+	line: '1_23.5',
+	tokens: [
+		{ startIndex: 0, type: 'number.float.cs' }
+	]}],
+
 	[{
 	line: '23.5e3',
 	tokens: [
@@ -568,6 +605,12 @@ testTokenization('csharp', [
 		{ startIndex: 0, type: 'number.float.cs' }
 	]}],
 
+	[{
+	line: '2_3.5f',
+	tokens: [
+		{ startIndex: 0, type: 'number.float.cs' }
+	]}],
+
 	[{
 	line: '1.72E3F',
 	tokens: [
@@ -598,6 +641,12 @@ testTokenization('csharp', [
 		{ startIndex: 0, type: 'number.float.cs' }
 	]}],
 
+	[{
+	line: '456_123.5D',
+	tokens: [
+		{ startIndex: 0, type: 'number.float.cs' }
+	]}],
+
 	[{
 	line: '23.5d',
 	tokens: [
@@ -616,6 +665,12 @@ testTokenization('csharp', [
 		{ startIndex: 0, type: 'number.float.cs' }
 	]}],
 
+	[{
+	line: '1.720_123E3d',
+	tokens: [
+		{ startIndex: 0, type: 'number.float.cs' }
+	]}],
+
 	[{
 	line: '1.72e3D',
 	tokens: [