ParseImplicitIncludeInfo: add Fortran implicit include handling
Currently cmake is only setting CMAKE_Fortran_IMPLICIT_INCLUDE_DIRECTORIES the first time it runs (the implicit includes parser is only run when the cache variables are initially populated). It is left unset during additional runs. This behavior is both confusing and inconsistent. Modify CMakeFortranCompiler.cmake.in to preserve the value of CMAKE_Fortran_IMPLICIT_INCLUDE_DIRECTORIES so that cmake's Fortran behavior matches C and CXX (i.e. CMAKE_Fortran_IMPLICIT_INCLUDE_DIRECTORIES retains its value across runs). The implicit includes variable may not be as useful for Fortran as it is for C and CXX, but we do want cmake to be consistent in how it is handled. Adjust CMakeParseImplicitIncludeInfo to parse verbose Fortran output for Cray and XL compiler IDs (GNU and clang were already ok since they use the same verbose output format as they do with C/CXX). Allow Tests/RunCMake/ParseImplicitIncludeInfo/data/CMakeLists.txt to generate test inputs for Fortran too, and add some sample Fortran input files for the Tests/RunCMake/ParseImplicitIncludeInfo test.