message: build: bump version to 4.3.0rc1
diff: dnl require autoconf 2.60 (AS_ECHO/AS_ECHO_N)
  AC_PREREQ([2.60])
  define(_CLIENT_VERSION_MAJOR, 4)
  -define(_CLIENT_VERSION_MINOR, 2)
  -define(_CLIENT_VERSION_REVISION, 99)
  +define(_CLIENT_VERSION_MINOR, 3)
  +define(_CLIENT_VERSION_REVISION, 0)
  define(_CLIENT_VERSION_BUILD, 0)
  -define(_CLIENT_VERSION_RC, 0)
  -define(_CLIENT_VERSION_IS_RELEASE, false)
  +define(_CLIENT_VERSION_RC, 1)
  +define(_CLIENT_VERSION_IS_RELEASE, true)
  define(_COPYRIGHT_YEAR, 2020)
  AC_INIT([PIVX Core],m4_join([.], _CLIENT_VERSION_MAJOR, _CLIENT_VERSION_MINOR, _CLIENT_VERSION_REVISION, m4_if(_CLIENT_VERSION_BUILD, [0], [], _CLIENT_VERSION_BUILD))m4_if(_CLIENT_VERSION_RC, [0], [], [rc]_CLIENT_VERSION_RC),[https://github.com/pivx-project/pivx/issues],[pivx],[https://pivx.org/])
  AC_CONFIG_SRCDIR([src/main.cpp])
  