cgo: support function-like macros

This is needed for code like this:

    #define __WASI_ERRNO_INVAL (UINT16_C(28))
    #define EINVAL __WASI_ERRNO_INVAL

cgo/testdata/const.go

@@ -3,13 +3,26 @@ package main
 /*
 #define foo 3
 #define bar foo
+
 #define unreferenced 4
 #define referenced unreferenced
+
+#define fnlike() 5
+#define fnlike_val fnlike()
+#define square(n) (n*n)
+#define square_val square(20)
+#define add(a, b) (a + b)
+#define add_val add(3, 5)
 */
 import "C"
 
 const (
 	Foo = C.foo
 	Bar = C.bar
+
 	Baz = C.referenced
+
+	fnlike = C.fnlike_val
+	square = C.square_val
+	add    = C.add_val
 )

cgo/testdata/const.out.go

@@ -49,3 +49,6 @@ const C.foo = 3
 const C.bar = C.foo
 const C.unreferenced = 4
 const C.referenced = C.unreferenced
+const C.fnlike_val = 5
+const C.square_val = (20 * 20)
+const C.add_val = (3 + 5)

cgo/testdata/errors.go

@@ -26,6 +26,11 @@ import "C"
 // #warning another warning
 import "C"
 
+// #define add(a, b) (a+b)
+// #define add_toomuch add(1, 2, 3)
+// #define add_toolittle add(1)
+import "C"
+
 // Make sure that errors for the following lines won't change with future
 // additions to the CGo preamble.
 //
@@ -51,4 +56,7 @@ var (
 	// constants passed by a command line parameter
 	_ = C.SOME_PARAM_CONST_invalid
 	_ = C.SOME_PARAM_CONST_valid
+
+	_ = C.add_toomuch
+	_ = C.add_toolittle
 )

cgo/testdata/errors.out.go

@@ -7,6 +7,8 @@
 //     testdata/errors.go:16:33: unexpected token ), expected end of expression
 //     testdata/errors.go:17:34: unexpected token ), expected end of expression
 //     -: unexpected token INT, expected end of expression
+//     testdata/errors.go:30:35: unexpected number of parameters: expected 2, got 3
+//     testdata/errors.go:31:31: unexpected number of parameters: expected 2, got 1
 
 // Type checking errors after CGo processing:
 //     testdata/errors.go:102: cannot use 2 << 10 (untyped int constant 2048) as C.char value in variable declaration (overflows)
@@ -17,6 +19,8 @@
 //     testdata/errors.go:114: undefined: C.SOME_CONST_b
 //     testdata/errors.go:116: undefined: C.SOME_CONST_startspace
 //     testdata/errors.go:119: undefined: C.SOME_PARAM_CONST_invalid
+//     testdata/errors.go:122: undefined: C.add_toomuch
+//     testdata/errors.go:123: undefined: C.add_toolittle
 
 package main