Merge #1017

1017: attr-visitor: Split in its own source and header r=CohenArthur a=CohenArthur

Split up the 4000 lines rust-macro-expand.cc file containing the
AttrVisitor class and the macro expander implementation


Co-authored-by: Arthur Cohen <[email protected]>

Author: bors[bot]

gcc/rust/Make-lang.in

@@ -74,6 +74,7 @@ GRS_OBJS = \
     rust/rust-mangle.o \
     rust/rust-compile-resolve-path.o \
     rust/rust-macro-expand.o \
+    rust/rust-attribute-visitor.o \
     rust/rust-macro-invoc-lexer.o \
     rust/rust-macro-substitute-ctx.o \
     rust/rust-macro-builtins.o \