add std namespace prefix to common methods

Standard clib methods should be explicitly grabbed from the standard
namespace.

Change-Id: I8bcfcb260a99180d535ec8102c1a24c318cbc209
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/groupext.cpp b/groupext.cpp
index c69d910..43656cd 100644
--- a/groupext.cpp
+++ b/groupext.cpp
@@ -2,6 +2,8 @@
 
 #include <host-ipmid/ipmid-api.h>
 
+#include <cstdio>
+
 #define GRPEXT_GET_GROUP_CMD 0
 void register_netfn_groupext_functions() __attribute__((constructor));
 
@@ -13,7 +15,7 @@
     ipmi_ret_t rc = IPMI_CC_OK;
     uint8_t* p = (uint8_t*)response;
 
-    printf("IPMI GROUP EXTENSIONS\n");
+    std::printf("IPMI GROUP EXTENSIONS\n");
 
     *data_len = 1;
     *p = 0;