Add aligned_alloc to libc.

Bug: 72969374

Test: Bionic unit tests pass.
Test: Malloc debug unit tests pass.
Change-Id: I235985bbc638855d94249c97c98f14ab2924bda0
(cherry picked from commit d69ee59594088c0d92ba9273188ef53ea5e6cd6a)
diff --git a/libc/malloc_debug/README.md b/libc/malloc_debug/README.md
index b7a12a5..69d0648 100644
--- a/libc/malloc_debug/README.md
+++ b/libc/malloc_debug/README.md
@@ -23,6 +23,7 @@
 * `realloc`
 * `posix_memalign`
 * `memalign`
+* `aligned_alloc`
 * `malloc_usable_size`
 
 On 32 bit systems, these two deprecated functions are also replaced:
@@ -324,6 +325,10 @@
 
 **THREAD\_ID**: memalign pointer alignment size
 
+pointer = aligned\_alloc(alignment, size)
+
+**THREAD\_ID**: memalign pointer alignment size
+
 posix\_memalign(&pointer, alignment, size)
 
 **THREAD\_ID**: memalign pointer alignment size