[libc][math][c23] add c23 floating point fmaximum and fminimum functions. (#86016)

Fixes https://github.com/llvm/llvm-project/issues/85496.

---------

Co-authored-by: Job Hernandez <h93@protonmail.com>
diff --git a/libc/src/math/fminimumf.h b/libc/src/math/fminimumf.h
new file mode 100644
index 0000000..424309f
--- /dev/null
+++ b/libc/src/math/fminimumf.h
@@ -0,0 +1,19 @@
+//===-- Implementation header for fminimumf -------------------------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_MATH_FMINIMUMF_H
+#define LLVM_LIBC_SRC_MATH_FMINIMUMF_H
+
+namespace LIBC_NAMESPACE {
+
+float fminimumf(float x, float y);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_FMINIMUMF_H