Increase memory for task allJavaDoc to avoid OOM during building

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1888793 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/build.gradle b/build.gradle
index d8a089b..882df1b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -288,7 +288,7 @@
 	// for possible settings see https://docs.gradle.org/current/dsl/org.gradle.api.tasks.javadoc.Javadoc.html
 	classpath = files(subprojects.collect { it.sourceSets.main.compileClasspath })
 	destinationDir = file("${buildDir}/docs/javadoc")
-	maxMemory="384M"
+	maxMemory="768M"
 
 	// for possible options see https://docs.gradle.org/current/javadoc/org/gradle/external/javadoc/StandardJavadocDocletOptions.html
 	options.use = true