Update AAPCS and AAPCS64 links.

The old ones disappeared. Switch to the developer.arm.com pointers.
Hopefully they are more stable. (Interestingly, the "Download PDF" link
for AAPCS64 now points to a GitHub repo.)

Change-Id: Ifa81e95978285409a6323f007d041515d4f270ee
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/39006
Reviewed-by: Adam Langley <agl@google.com>

crypto/test/abi_test.h

diff --git a/crypto/test/abi_test.h b/crypto/test/abi_test.h
index a3c4bb8..d65c7f8 100644
--- a/crypto/test/abi_test.h
+++ b/crypto/test/abi_test.h
@@ -107,7 +107,7 @@
 #elif defined(OPENSSL_ARM)
 
 // References:
-// AAPCS: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf
+// AAPCS: https://developer.arm.com/docs/ihi0042/latest
 // iOS32: https://developer.apple.com/library/archive/documentation/Xcode/Conceptual/iPhoneOSABIReference/Articles/ARMv6FunctionCallingConventions.html
 // Linux: http://sourcery.mentor.com/sgpp/lite/arm/portal/kbattach142/arm_gnu_linux_%20abi.pdf
 //
@@ -146,7 +146,7 @@
 #elif defined(OPENSSL_AARCH64)
 
 // References:
-// AAPCS64: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf
+// AAPCS64: https://developer.arm.com/docs/ihi0055/latest
 // iOS64: https://developer.apple.com/library/archive/documentation/Xcode/Conceptual/iPhoneOSABIReference/Articles/ARM64FunctionCallingConventions.html
 //
 // In aarch64, r18 (accessed as w18 or x18 in a 64-bit context) is the platform