XL: Revert "Recognize compilers identified by __ibmxl__"

Revert commit eb1a9be4b6 (XL: Recognize compilers identified by
__ibmxl__, 2018-03-05, v3.11.0-rc3~4^2).  It is no longer needed because
we now use `__ibmxl__` to identify with compiler id `XLClang`.

Modules/Compiler/IBMCPP-C-DetermineVersionInternal.cmake

@@ -1,14 +1,6 @@
 
 set(_compiler_id_version_compute "
-# if defined(__ibmxl__)
-#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__ibmxl_version__)
-#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__ibmxl_release__)
-#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__ibmxl_modification__)
-#  define @PREFIX@COMPILER_VERSION_TWEAK @MACRO_DEC@(__ibmxl_ptf_fix_level__)
-# else
-   /* __IBMC__ = VRP */
-#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__IBMC__/100)
-#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__IBMC__/10 % 10)
-#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__IBMC__    % 10)
-# endif
-")
+  /* __IBMC__ = VRP */
+# define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__IBMC__/100)
+# define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__IBMC__/10 % 10)
+# define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__IBMC__    % 10)")

Modules/Compiler/IBMCPP-CXX-DetermineVersionInternal.cmake

@@ -1,14 +1,6 @@
 
 set(_compiler_id_version_compute "
-# if defined(__ibmxl__)
-#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__ibmxl_version__)
-#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__ibmxl_release__)
-#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__ibmxl_modification__)
-#  define @PREFIX@COMPILER_VERSION_TWEAK @MACRO_DEC@(__ibmxl_ptf_fix_level__)
-# else
-   /* __IBMCPP__ = VRP */
-#  define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__IBMCPP__/100)
-#  define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__IBMCPP__/10 % 10)
-#  define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__IBMCPP__    % 10)
-# endif
-")
+  /* __IBMCPP__ = VRP */
+# define @PREFIX@COMPILER_VERSION_MAJOR @MACRO_DEC@(__IBMCPP__/100)
+# define @PREFIX@COMPILER_VERSION_MINOR @MACRO_DEC@(__IBMCPP__/10 % 10)
+# define @PREFIX@COMPILER_VERSION_PATCH @MACRO_DEC@(__IBMCPP__    % 10)")

Modules/Compiler/XL-C-DetermineCompiler.cmake

@@ -1,4 +1,4 @@
 
-set(_compiler_id_pp_test "defined(__ibmxl__) || (defined(__IBMC__) && !defined(__COMPILER_VER__) && __IBMC__ >= 800)")
+set(_compiler_id_pp_test "defined(__IBMC__) && !defined(__COMPILER_VER__) && __IBMC__ >= 800")
 
 include("${CMAKE_CURRENT_LIST_DIR}/IBMCPP-C-DetermineVersionInternal.cmake")

Modules/Compiler/XL-CXX-DetermineCompiler.cmake

@@ -1,4 +1,4 @@
 
-set(_compiler_id_pp_test "defined(__ibmxl__) || (defined(__IBMCPP__) && !defined(__COMPILER_VER__) && __IBMCPP__ >= 800)")
+set(_compiler_id_pp_test "defined(__IBMCPP__) && !defined(__COMPILER_VER__) && __IBMCPP__ >= 800")
 
 include("${CMAKE_CURRENT_LIST_DIR}/IBMCPP-CXX-DetermineVersionInternal.cmake")