syntax: go: highlight also floats with leading zeroes as valid

See the discussion on the mailing list:
https://lists.gnu.org/archive/html/nano-devel/2018-01/msg00022.html
https://lists.gnu.org/archive/html/nano-devel/2018-02/msg00090.html

Signed-off-by: Tom Levy <tomlevy93@gmail.com>

syntax/go.nanorc

@@ -24,9 +24,11 @@ color brightcyan "\<(package|import)\>"
 color brightcyan "//[[:space:]]*\+build[[:space:]]+(([a-zA-Z_0-9]+[[:space:]]*)+,[[:space:]]*)*[a-zA-Z_0-9]+"
 
 # Literals.
-color red "\<0([0-7]*|[xX][0-9a-fA-F]+)\>"
-color red "(\<0+|\B)\.[0-9]+([Ee][+-]?[0-9]+)?i?\>"
-color red "\<[1-9][0-9]*(\.[0-9]*)?([Ee][+-]?[0-9]+)?i?\>"
+color red "\<([1-9][0-9]*|0[0-7]*|0[xX][0-9A-Fa-f]+)\>"
+color red "\<[0-9]+\.[0-9]*([eE][+-]?[0-9]+)?i?\>"
+color red "\<[0-9]+[eE][+-]?[0-9]+i?\>"
+color red "\B\.[0-9]+([eE][+-]?[0-9]+)?i?\>"
+color red "\<[0-9]+i\>"
 
 # Strings and characters; slightly fuzzy.
 color red "\<(true|false|nil|iota|_)\>"