Enable -Wformat-security warning and cleanup GYP.

Enable the -Wformat-security and -Wformat warnings for talk/.

Remove *.def and *.h.pump files from webrtc/base/base.gyp since they're not supported by some tools.

BUG=4242
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/49969004

Cr-Commit-Position: refs/heads/master@{#9191}
diff --git a/talk/build/common.gypi b/talk/build/common.gypi
index 4735bc8..87f852c 100644
--- a/talk/build/common.gypi
+++ b/talk/build/common.gypi
@@ -88,11 +88,17 @@
           'LINUX',
           'WEBRTC_LINUX',
         ],
+        # Remove Chromium's disabling of the -Wformat warning.
+        'cflags!': [
+          '-Wno-format',
+        ],
         'conditions': [
           ['clang==1', {
             'cflags': [
               '-Wall',
               '-Wextra',
+              '-Wformat',
+              '-Wformat-security',
               '-Wimplicit-fallthrough',
               '-Wmissing-braces',
               '-Wreorder',
diff --git a/webrtc/base/base.gyp b/webrtc/base/base.gyp
index 76d85a7..377b41c 100644
--- a/webrtc/base/base.gyp
+++ b/webrtc/base/base.gyp
@@ -127,9 +127,7 @@
         'base64.h',
         'basicdefs.h',
         'bind.h',
-        'bind.h.pump',
         'callback.h',
-        'callback.h.pump',
         'common.cc',
         'common.h',
         'cpumonitor.cc',
@@ -176,9 +174,7 @@
         'json.cc',
         'json.h',
         'latebindingsymboltable.cc',
-        'latebindingsymboltable.cc.def',
         'latebindingsymboltable.h',
-        'latebindingsymboltable.h.def',
         'libdbusglibsymboltable.cc',
         'libdbusglibsymboltable.h',
         'linux.cc',
@@ -382,9 +378,7 @@
             'bandwidthsmoother.cc',
             'bandwidthsmoother.h',
             'bind.h',
-            'bind.h.pump',
             'callback.h',
-            'callback.h.pump',
             'constructormagic.h',
             'dbus.cc',
             'dbus.h',
@@ -394,15 +388,12 @@
             'filelock.h',
             'fileutils_mock.h',
             'genericslot.h',
-            'genericslot.h.pump',
             'httpserver.cc',
             'httpserver.h',
             'json.cc',
             'json.h',
             'latebindingsymboltable.cc',
-            'latebindingsymboltable.cc.def',
             'latebindingsymboltable.h',
-            'latebindingsymboltable.h.def',
             'libdbusglibsymboltable.cc',
             'libdbusglibsymboltable.h',
             'linuxfdwalk.c',