Modules: Format documentation to avoid over-long preformatted lines

Convert several preformatted code block literals that enumerate lists of
options or variables to use reST definition lists instead.  Manually
wrap other long lines in code blocks.

Modules/FindBacktrace.cmake

@@ -5,18 +5,24 @@
 # Find provider for backtrace(3).
 #
 # Checks if OS supports backtrace(3) via either libc or custom library.
-# This module defines the following variables::
+# This module defines the following variables:
 #
-#  Backtrace_HEADER       - The header file needed for backtrace(3). Cached.
-#                           Could be forcibly set by user.
-#  Backtrace_INCLUDE_DIRS - The include directories needed to use backtrace(3) header.
-#  Backtrace_LIBRARIES    - The libraries (linker flags) needed to use backtrace(3), if any.
-#  Backtrace_FOUND        - Is set if and only if backtrace(3) support detected.
+# ``Backtrace_HEADER``
+#   The header file needed for backtrace(3). Cached.
+#   Could be forcibly set by user.
+# ``Backtrace_INCLUDE_DIRS``
+#   The include directories needed to use backtrace(3) header.
+# ``Backtrace_LIBRARIES``
+#   The libraries (linker flags) needed to use backtrace(3), if any.
+# ``Backtrace_FOUND``
+#   Is set if and only if backtrace(3) support detected.
 #
-# The following cache variables are also available to set or use::
+# The following cache variables are also available to set or use:
 #
-#  Backtrace_LIBRARY     - The external library providing backtrace, if any.
-#  Backtrace_INCLUDE_DIR - The directory holding the backtrace(3) header.
+# ``Backtrace_LIBRARY``
+#   The external library providing backtrace, if any.
+# ``Backtrace_INCLUDE_DIR``
+#   The directory holding the backtrace(3) header.
 #
 # Typical usage is to generate of header file using configure_file() with the
 # contents like the following::