Update version to 4.3a1

Author: dellaert

CMakeLists.txt

@@ -7,7 +7,7 @@ endif()
 set (GTSAM_VERSION_MAJOR 4)
 set (GTSAM_VERSION_MINOR 3)
 set (GTSAM_VERSION_PATCH 0)
-set (GTSAM_PRERELEASE_VERSION "a0")
+set (GTSAM_PRERELEASE_VERSION "a1")
 math (EXPR GTSAM_VERSION_NUMERIC "10000 * ${GTSAM_VERSION_MAJOR} + 100 * ${GTSAM_VERSION_MINOR} + ${GTSAM_VERSION_PATCH}")
 
 # Set the version string for the library.