[macppc] Unbreak emulators/retroarch

Hi!

> http://build-failures.rhaalovely.net/powerpc/2019-07-14/emulators/retroarch.log

It's simply a missing header with the asm code that goes with it.

Once added it builds [0] and (surprisingly) runs fine on macppc. While
pretty useless to do in such a case, i've tested on amd64 as well, and
met no issues indeed.

Comments/feedback are welcome,

Charlène.


[0] https://bin.charlenew.xyz/retroarch.log.gz


Index: Makefile
===================================================================
RCS file: /cvs/ports/emulators/retroarch/Makefile,v
retrieving revision 1.18
diff -u -p -u -p -r1.18 Makefile
--- Makefile 12 Jul 2019 20:46:09 -0000 1.18
+++ Makefile 27 Jul 2019 15:15:30 -0000
@@ -5,7 +5,7 @@ COMMENT = generic multi-emulator fronte
V = 1.7.6
DISTNAME = RetroArch-$V
PKGNAME = retroarch-$V
-REVISION = 1
+REVISION = 2

CATEGORIES = emulators

Index: patches/patch-libretro-common_features_features_cpu_c
===================================================================
RCS file: patches/patch-libretro-common_features_features_cpu_c
diff -N patches/patch-libretro-common_features_features_cpu_c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-libretro-common_features_features_cpu_c 27 Jul 2019 15:15:30 -0000
@@ -0,0 +1,17 @@
+$OpenBSD$
+
+ppc fix for:
+features_cpu.c:(.text+0x20): undefined reference to `__mftb'
+
+Index: libretro-common/features/features_cpu.c
+--- libretro-common/features/features_cpu.c.orig
++++ libretro-common/features/features_cpu.c
+@@ -39,7 +39,7 @@
+ #include <windows.h>
+