FindLATEX: Use FPHSA to report status in standard way

Otherwise LaTeX was marked as not found in the summary.
Also revise the documentation.

Modules/FindLATEX.cmake

@@ -4,8 +4,9 @@
 #
 # Find Latex
 #
-# This module finds if Latex is installed and determines where the
-# executables are.  This code sets the following variables:
+# This module finds an installed Latex and determines the location
+# of the compiler.  Additionally the module looks for Latex-related
+# software like BibTeX.  This code sets the following variables:
 #
 # ::
 #
@@ -18,7 +19,7 @@
 #   LATEX2HTML_CONVERTER: path to the LaTeX2Html converter
 
 #=============================================================================
-# Copyright 2002-2009 Kitware, Inc.
+# Copyright 2002-2014 Kitware, Inc.
 #
 # Distributed under the OSI-approved BSD License (the "License");
 # see accompanying file Copyright.txt for details.
@@ -131,3 +132,8 @@ mark_as_advanced(
   PS2PDF_CONVERTER
   LATEX2HTML_CONVERTER
 )
+
+include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
+find_package_handle_standard_args(Latex
+  REQUIRED_VARS LATEX_COMPILER
+)