Raise minimum supported Java version to 7

Changes to keyboard handling require methods from the KeyEvent
class that were not introduced until Java 7.
diff --git a/BUILDING.txt b/BUILDING.txt
index 9449810..86fb45d 100644
--- a/BUILDING.txt
+++ b/BUILDING.txt
@@ -57,7 +57,7 @@
 Build Requirements (Java)
 =========================
 
--- Sun/Oracle JDK v5 or later or OpenJDK
+-- Sun/Oracle JDK 1.7 or later or OpenJDK 7 or later
 
 -- See "Building Java Support" below.
 
diff --git a/java/CMakeLists.txt b/java/CMakeLists.txt
index ecf86b0..80e0dd2 100644
--- a/java/CMakeLists.txt
+++ b/java/CMakeLists.txt
@@ -9,7 +9,7 @@
 
 set(DATA_DIR "${CMAKE_INSTALL_PREFIX}/share")
 
-set(DEFAULT_JAVACFLAGS "-source 1.6 -target 1.6 -Xlint:all,-serial,-cast,-unchecked,-fallthrough,-dep-ann,-deprecation,-rawtypes")
+set(DEFAULT_JAVACFLAGS "-source 7 -target 7 -Xlint:all,-serial,-cast,-unchecked,-fallthrough,-dep-ann,-deprecation,-rawtypes")
 set(JAVACFLAGS ${DEFAULT_JAVACFLAGS} CACHE STRING
   "Java compiler flags (Default: ${DEFAULT_JAVACFLAGS})")
 message(STATUS "Java compiler flags = ${JAVACFLAGS}")