Introduce and export hotfix version component

The cmake variable PROJECT_VERSION_HOTFIX contains the hotfix version
component. 0 means no hotfix, 1 means the first hotfix, 2 the second,
and so on.

cmake/FairMQConfig.cmake.in

@@ -23,6 +23,7 @@ set_and_check(@PROJECT_NAME@_CMAKEMODDIR @PACKAGE_CMAKE_INSTALL_PREFIX@/@PROJECT
 set(@PROJECT_NAME@_CXX_STANDARD_REQUIRED @CMAKE_CXX_STANDARD_REQUIRED@)
 set(@PROJECT_NAME@_CXX_STANDARD @CMAKE_CXX_STANDARD@)
 set(@PROJECT_NAME@_CXX_EXTENSIONS @CMAKE_CXX_EXTENSIONS@)
+set(@PROJECT_NAME@_VERSION_HOTFIX @PROJECT_VERSION_HOTFIX@)
 
 ### Import cmake modules
 set(CMAKE_MODULE_PATH ${@PROJECT_NAME@_CMAKEMODDIR} ${CMAKE_MODULE_PATH})

cmake/FairMQLib.cmake

@@ -180,6 +180,12 @@ macro(set_fairmq_defaults)
     # Rationale in https://github.com/ninja-build/ninja/issues/814
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fdiagnostics-color=always")
   endif()
+
+  if(NOT PROJECT_VERSION_TWEAK)
+    set(PROJECT_VERSION_HOTFIX 0)
+  else()
+    set(PROJECT_VERSION_HOTFIX ${PROJECT_VERSION_TWEAK})
+  endif()
 endmacro()
 
 function(join VALUES GLUE OUTPUT)

fairmq/Version.h.in

@@ -9,10 +9,14 @@
 #ifndef FAIR_MQ_VERSION_H
 
 #define FAIRMQ_VERSION "@PROJECT_VERSION@"
-#define FAIRMQ_VERSION_DEC (@PROJECT_VERSION_MAJOR@ * 10000) + (@PROJECT_VERSION_MINOR@ * 100) + @PROJECT_VERSION_PATCH@
+#define FAIRMQ_VERSION_DEC (@PROJECT_VERSION_MAJOR@ * 100000) \
+                           + (@PROJECT_VERSION_MINOR@ * 1000) \
+                           + (@PROJECT_VERSION_PATCH@ * 10) \
+                           + @PROJECT_VERSION_HOTFIX@
 #define FAIRMQ_VERSION_MAJOR @PROJECT_VERSION_MAJOR@
 #define FAIRMQ_VERSION_MINOR @PROJECT_VERSION_MINOR@
 #define FAIRMQ_VERSION_PATCH @PROJECT_VERSION_PATCH@
+#define FAIRMQ_VERSION_HOTFIX @PROJECT_VERSION_HOTFIX@
 #define FAIRMQ_GIT_VERSION "@PROJECT_GIT_VERSION@"
 #define FAIRMQ_GIT_DATE "@PROJECT_GIT_DATE@"
 #define FAIRMQ_REPO_URL "https://github.com/FairRootGroup/FairMQ"