vpx_ports: add extern "C" to headers

Change-Id: Iba9b198ce78b3f8b644feba064f83abc247e75dd
diff --git a/vpx_ports/arm.h b/vpx_ports/arm.h
index 2562d9c..1e4a8e2 100644
--- a/vpx_ports/arm.h
+++ b/vpx_ports/arm.h
@@ -14,6 +14,10 @@
 #include <stdlib.h>
 #include "vpx_config.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*ARMv5TE "Enhanced DSP" instructions.*/
 #define HAS_EDSP  0x01
 /*ARMv6 "Parallel" or "Media" instructions.*/
@@ -23,5 +27,9 @@
 
 int arm_cpu_caps(void);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  // VPX_PORTS_ARM_H_
 
diff --git a/vpx_ports/x86.h b/vpx_ports/x86.h
index a9d51a3..603e2b6 100644
--- a/vpx_ports/x86.h
+++ b/vpx_ports/x86.h
@@ -14,6 +14,10 @@
 #include <stdlib.h>
 #include "vpx_config.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 typedef enum {
   VPX_CPU_UNKNOWN = -1,
   VPX_CPU_AMD,
@@ -256,5 +260,9 @@
 
 
 extern void vpx_reset_mmx_state(void);
-#endif  // VPX_PORTS_X86_H_
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // VPX_PORTS_X86_H_