Allow prefix calls with .:< ... > on integer literals

Fix Github #2094. Before this commit, '42.:<->' would error because the
check which prevented integers ending with fullstops was overly
aggressive: any time an integer was followed by '.:', an error would be
generated. With this commit, an integer followed by '.:' will only error
if the next thing after it is not '<' then a prefix operator then '>'

src/Perl6/Grammar.nqp

@@ -3688,7 +3688,7 @@ grammar Perl6::Grammar is HLL::Grammar does STD {
             ]
         | <VALUE=decint>
         ]
-        <!!before ['.' <?before \s | ',' | '=' | ':' | <.terminator> | $ > <.typed_sorry: 'X::Syntax::Number::IllegalDecimal'>]? >
+        <!!before ['.' <?before \s | ',' | '=' | ':' <!before ['<' <OPER=prefix> '>'] > | <.terminator> | $ > <.typed_sorry: 'X::Syntax::Number::IllegalDecimal'>]? >
         [ <?before '_' '_'+\d> <.sorry: "Only isolated underscores are allowed inside numbers"> ]?
     }