hcl/hclsyntax: Fix scanning of multi-line comments

The pattern here was being too greedy because by default the longest match
is taken, and "*/" followed by more content is always longer than just
the "*/" to terminate the match.

The :>> symbol is a "finish guard" which tells Ragel to prefer to exit
from any* as soon as "*/" matches, making the match ungreedy.

The result of this is that input files containing more than one multi-line
comment will now tokenize each one separately, whereas before we would
create one long comment including everything from the first /* to the
final */ in the file, effectively causing parts of the file to be
ignored entirely.

hcl/hclsyntax/scan_tokens.rl

@@ -60,7 +60,7 @@ func scanTokens(data []byte, filename string, start hcl.Pos, mode scanMode) []To
         Comment = (
             ("#" (any - EndOfLine)* EndOfLine) |
             ("//" (any - EndOfLine)* EndOfLine) |
-            ("/*" any* "*/")
+            ("/*" any* :>> "*/")
         );
 
         # Note: hclwrite assumes that only ASCII spaces appear between tokens,

hcl/hclsyntax/scan_tokens_test.go

@@ -1526,6 +1526,43 @@ EOF
 				},
 			},
 		},
+		{
+			"/* hello */ howdy /* hey */",
+			[]Token{
+				{
+					Type:  TokenComment,
+					Bytes: []byte("/* hello */"),
+					Range: hcl.Range{
+						Start: hcl.Pos{Byte: 0, Line: 1, Column: 1},
+						End:   hcl.Pos{Byte: 11, Line: 1, Column: 12},
+					},
+				},
+				{
+					Type:  TokenIdent,
+					Bytes: []byte("howdy"),
+					Range: hcl.Range{
+						Start: hcl.Pos{Byte: 12, Line: 1, Column: 13},
+						End:   hcl.Pos{Byte: 17, Line: 1, Column: 18},
+					},
+				},
+				{
+					Type:  TokenComment,
+					Bytes: []byte("/* hey */"),
+					Range: hcl.Range{
+						Start: hcl.Pos{Byte: 18, Line: 1, Column: 19},
+						End:   hcl.Pos{Byte: 27, Line: 1, Column: 28},
+					},
+				},
+				{
+					Type:  TokenEOF,
+					Bytes: []byte{},
+					Range: hcl.Range{
+						Start: hcl.Pos{Byte: 27, Line: 1, Column: 28},
+						End:   hcl.Pos{Byte: 27, Line: 1, Column: 28},
+					},
+				},
+			},
+		},
 
 		// Invalid things
 		{