CheckSymbolExists: Convert docs to bracket comment syntax

Modules/CheckSymbolExists.cmake

@@ -1,38 +1,39 @@
 # Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
 # file Copyright.txt or https://cmake.org/licensing for details.
 
-#.rst:
-# CheckSymbolExists
-# -----------------
-#
-# Check if a symbol exists as a function, variable, or macro
-#
-# CHECK_SYMBOL_EXISTS(<symbol> <files> <variable>)
-#
-# Check that the <symbol> is available after including given header
-# <files> and store the result in a <variable>.  Specify the list of
-# files in one argument as a semicolon-separated list.
-# <variable> will be created as an internal cache variable.
-#
-# If the header files define the symbol as a macro it is considered
-# available and assumed to work.  If the header files declare the symbol
-# as a function or variable then the symbol must also be available for
-# linking.  If the symbol is a type or enum value it will not be
-# recognized (consider using CheckTypeSize or CheckCSourceCompiles).  If
-# the check needs to be done in C++, consider using
-# CHECK_CXX_SYMBOL_EXISTS(), which does the same as
-# CHECK_SYMBOL_EXISTS(), but in C++.
-#
-# The following variables may be set before calling this macro to modify
-# the way the check is run:
-#
-# ::
-#
-#   CMAKE_REQUIRED_FLAGS = string of compile command line flags
-#   CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
-#   CMAKE_REQUIRED_INCLUDES = list of include directories
-#   CMAKE_REQUIRED_LIBRARIES = list of libraries to link
-#   CMAKE_REQUIRED_QUIET = execute quietly without messages
+#[=======================================================================[.rst:
+CheckSymbolExists
+-----------------
+
+Check if a symbol exists as a function, variable, or macro
+
+CHECK_SYMBOL_EXISTS(<symbol> <files> <variable>)
+
+Check that the <symbol> is available after including given header
+<files> and store the result in a <variable>.  Specify the list of
+files in one argument as a semicolon-separated list.
+<variable> will be created as an internal cache variable.
+
+If the header files define the symbol as a macro it is considered
+available and assumed to work.  If the header files declare the symbol
+as a function or variable then the symbol must also be available for
+linking.  If the symbol is a type or enum value it will not be
+recognized (consider using CheckTypeSize or CheckCSourceCompiles).  If
+the check needs to be done in C++, consider using
+CHECK_CXX_SYMBOL_EXISTS(), which does the same as
+CHECK_SYMBOL_EXISTS(), but in C++.
+
+The following variables may be set before calling this macro to modify
+the way the check is run:
+
+::
+
+  CMAKE_REQUIRED_FLAGS = string of compile command line flags
+  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
+  CMAKE_REQUIRED_INCLUDES = list of include directories
+  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
+  CMAKE_REQUIRED_QUIET = execute quietly without messages
+#]=======================================================================]
 
 macro(CHECK_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
   if(CMAKE_C_COMPILER_LOADED)