Document and test allowlisting and blocklisting methods (#2344)

Author: pvdrz

bindgen-tests/tests/expectations/tests/blocklist-methods.rs

@@ -0,0 +1,8 @@
+// bindgen-flags: --blocklist-function="Foo_ba.*"
+
+class Foo {
+    public:
+        int foo();
+        int bar();
+        int baz();
+};

bindgen-tests/tests/headers/blocklist-methods.hpp

@@ -850,6 +850,10 @@ impl Builder {
     /// Hide the given function from the generated bindings. Regular expressions
     /// are supported.
     ///
+    /// Methods can be blocklisted by prefixing the name of the type implementing
+    /// them followed by an underscore. So if `Foo` has a method `bar`, it can
+    /// be blocklisted as `Foo_bar`.
+    ///
     /// To blocklist functions prefixed with "mylib" use `"mylib_.*"`.
     /// For more complicated expressions check
     /// [regex](https://docs.rs/regex/*/regex/) docs
@@ -929,6 +933,10 @@ impl Builder {
     /// transitively refers to) appears in the generated bindings. Regular
     /// expressions are supported.
     ///
+    /// Methods can be allowlisted by prefixing the name of the type
+    /// implementing them followed by an underscore. So if `Foo` has a method
+    /// `bar`, it can be allowlisted as `Foo_bar`.
+    ///
     /// To allowlist functions prefixed with "mylib" use `"mylib_.*"`.
     /// For more complicated expressions check
     /// [regex](https://docs.rs/regex/*/regex/) docs