Drop 'static for pub const strings

Constant and static declaration have a 'static live time by default,
that is already elided since 1.17.

Clippy complains on this kind of strings that are present in the
generated code.

This patch remove the 'static live time for those strings.

Fix rust-lang#1612

Signed-off-by: Alberto Planas <[email protected]>

Author: aplanas

src/codegen/mod.rs

@@ -668,7 +668,7 @@ impl CodeGenerator for Var {
                             let cstr = helpers::ast_ty::cstr_expr(string);
                             result.push(quote! {
                                 #(#attrs)*
-                                pub const #canonical_ident : &'static #ty = #cstr ;
+                                pub const #canonical_ident : &#ty = #cstr ;
                             });
                         }
                         Err(..) => {