Improve dependencies checks in the build process

- Rename all Find*.cmake files to uppercase, to make things more consistent,
  and fix some issues with them (notably the REQUIRED flag)

- Rename SYSTEMDDAEMON to SYSTEMD and only use the libsystemd instead of
  libsystemd-daemon because it's deprecated for a long time now

- Provide a WITH_* and WITHOUT_* switch for all optional dependencies

- Document things in the INSTALL file

cmake/Modules/FindBOTAN.cmake

@@ -25,7 +25,7 @@ find_library(BOTAN_LIBRARIES NAMES botan botan-1.11
 # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
 # set BOTAN_FOUND to TRUE if these two variables are set.
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(Botan REQUIRED_VARS BOTAN_LIBRARIES BOTAN_INCLUDE_DIRS)
+find_package_handle_standard_args(BOTAN REQUIRED_VARS BOTAN_LIBRARIES BOTAN_INCLUDE_DIRS)
 
 if(BOTAN_FOUND)
   set(BOTAN_LIBRARY ${BOTAN_LIBRARIES})

cmake/Modules/FindSYSTEMD.cmake

@@ -0,0 +1,39 @@
+# - Find SystemdDaemon
+# Find the systemd daemon library
+#
+# This module defines the following variables:
+#   SYSTEMD_FOUND  -  True if library and include directory are found
+# If set to TRUE, the following are also defined:
+#   SYSTEMD_INCLUDE_DIRS  -  The directory where to find the header file
+#   SYSTEMD_LIBRARIES  -  Where to find the library file
+#
+# For conveniance, these variables are also set. They have the same values
+# than the variables above.  The user can thus choose his/her prefered way
+# to write them.
+#   SYSTEMD_LIBRARY
+#   SYSTEMD_INCLUDE_DIR
+#
+# This file is in the public domain
+
+include(FindPkgConfig)
+pkg_check_modules(SYSTEMD libsystemd)
+
+if(NOT SYSTEMD_FOUND)
+  find_path(SYSTEMD_INCLUDE_DIRS NAMES systemd/sd-daemon.h
+    DOC "The Systemd include directory")
+
+  find_library(SYSTEMD_LIBRARIES NAMES systemd
+    DOC "The Systemd library")
+
+  # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
+  # set SYSTEMD_FOUND to TRUE if these two variables are set.
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(SYSTEMD REQUIRED_VARS SYSTEMD_LIBRARIES SYSTEMD_INCLUDE_DIRS)
+
+  if(SYSTEMD_FOUND)
+    set(SYSTEMD_LIBRARY ${SYSTEMD_LIBRARIES})
+    set(SYSTEMD_INCLUDE_DIR ${SYSTEMD_INCLUDE_DIRS})
+  endif()
+endif()
+
+mark_as_advanced(SYSTEMD_INCLUDE_DIRS SYSTEMD_LIBRARIES)

cmake/Modules/FindSystemdDaemon.cmake

@@ -1,39 +0,0 @@
-# - Find SystemdDaemon
-# Find the systemd daemon library
-#
-# This module defines the following variables:
-#   SYSTEMDDAEMON_FOUND  -  True if library and include directory are found
-# If set to TRUE, the following are also defined:
-#   SYSTEMDDAEMON_INCLUDE_DIRS  -  The directory where to find the header file
-#   SYSTEMDDAEMON_LIBRARIES  -  Where to find the library file
-#
-# For conveniance, these variables are also set. They have the same values
-# than the variables above.  The user can thus choose his/her prefered way
-# to write them.
-#   SYSTEMDDAEMON_LIBRARY
-#   SYSTEMDDAEMON_INCLUDE_DIR
-#
-# This file is in the public domain
-
-include(FindPkgConfig)
-pkg_check_modules(SYSTEMDDAEMON libsystemd-daemon)
-
-if(NOT SYSTEMDDAEMON_FOUND)
-  find_path(SYSTEMDDAEMON_INCLUDE_DIRS NAMES systemd/sd-daemon.h
-    DOC "The Systemd Daemon include directory")
-
-  find_library(SYSTEMDDAEMON_LIBRARIES NAMES systemd-daemon systemd
-    DOC "The Systemd Daemon library")
-
-  # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
-  # set SYSTEMDDAEMON_FOUND to TRUE if these two variables are set.
-  include(FindPackageHandleStandardArgs)
-  find_package_handle_standard_args(SYSTEMDDAEMON REQUIRED_VARS SYSTEMDDAEMON_LIBRARIES SYSTEMDDAEMON_INCLUDE_DIRS)
-
-  if(SYSTEMDDAEMON_FOUND)
-    set(SYSTEMDDAEMON_LIBRARY ${SYSTEMDDAEMON_LIBRARIES})
-    set(SYSTEMDDAEMON_INCLUDE_DIR ${SYSTEMDDAEMON_INCLUDE_DIRS})
-  endif()
-endif()
-
-mark_as_advanced(SYSTEMDDAEMON_INCLUDE_DIRS SYSTEMDDAEMON_LIBRARIES)