GmsCore: disable battery optimizations for microG

Prevent battery optimization for GmsCore
* Add microG sysconfig
* Update GmsCore Android.mk
diff --git a/GmsCore/Android.mk b/GmsCore/Android.mk
index 1d5a928..1850971 100644
--- a/GmsCore/Android.mk
+++ b/GmsCore/Android.mk
@@ -9,6 +9,14 @@
 include $(BUILD_PREBUILT)
 
 include $(CLEAR_VARS)
+LOCAL_MODULE := sysconfig-com.google.android.gms.xml
+LOCAL_MODULE_TAGS := optional
+LOCAL_MODULE_CLASS := ETC
+LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/sysconfig
+LOCAL_SRC_FILES := $(LOCAL_MODULE)
+include $(BUILD_PREBUILT)
+
+include $(CLEAR_VARS)
 LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE := GmsCore
 LOCAL_SRC_FILES := com.google.android.gms-204714034.apk
@@ -18,5 +26,6 @@
 LOCAL_CERTIFICATE := PRESIGNED
 LOCAL_OVERRIDES_PACKAGES := com.qualcomm.location
 LOCAL_REQUIRED_MODULES := privapp-permissions-com.google.android.gms.xml
+LOCAL_REQUIRED_MODULES := sysconfig-com.google.android.gms.xml
 include $(BUILD_PREBUILT)
 
diff --git a/GmsCore/sysconfig-com.google.android.gms.xml b/GmsCore/sysconfig-com.google.android.gms.xml
new file mode 100644
index 0000000..12e719f
--- /dev/null
+++ b/GmsCore/sysconfig-com.google.android.gms.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2017-2018 ale5000
+     SPDX-License-Identifer: GPL-3.0-or-later
+-->
+
+<config>
+    <!-- microG GmsCore must always have network access for GCM. -->
+    <allow-in-power-save package="com.google.android.gms" />
+    <allow-in-data-usage-save package="com.google.android.gms" />
+    <allow-unthrottled-location package="com.google.android.gms" />
+</config>