Help: Document CMAKE_FIND_PACKAGE_NAME variable

Help/manual/cmake-variables.7.rst

@@ -36,6 +36,7 @@ Variables that Provide Information
    /variable/CMAKE_EXECUTABLE_SUFFIX
    /variable/CMAKE_EXTRA_GENERATOR
    /variable/CMAKE_EXTRA_SHARED_LIBRARY_SUFFIXES
+   /variable/CMAKE_FIND_PACKAGE_NAME
    /variable/CMAKE_GENERATOR
    /variable/CMAKE_GENERATOR_PLATFORM
    /variable/CMAKE_GENERATOR_TOOLSET

Help/variable/CMAKE_FIND_PACKAGE_NAME.rst

@@ -0,0 +1,6 @@
+CMAKE_FIND_PACKAGE_NAME
+-----------------------
+
+Defined by the :command:`find_package` command while loading
+a find module to record the caller-specified package name.
+See command documentation for details.