Add a procedural macro for expanding all function signatures

Introduce `libm_test::for_each_function`. which macro takes a callback
macro and invokes it once per function signature. This provides an
easier way of registering various tests and benchmarks without
duplicating the function names and signatures each time.

Author: tgross35

Cargo.toml

@@ -28,11 +28,13 @@ resolver = "2"
 members = [
   "crates/compiler-builtins-smoke-test",
   "crates/libm-bench",
+  "crates/libm-macros",
   "crates/libm-test",
   "crates/musl-math-sys",
 ]
 default-members = [
   ".",
+  "crates/libm-macros",
   "crates/libm-test",
 ]
 

crates/libm-macros/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "libm-macros"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0.88"
+quote = "1.0.37"
+syn = { version = "2.0.79", features = ["full", "extra-traits", "visit-mut"] }