Fix typos identified using codespell

See https://github.com/codespell-project/codespell#readme

The following command was used:

```
codespell -q6 --skip="\
.git,\
*.json,\
./Copyright.txt,\
./Help/command/foreach.rst,\
./Help/prop_test/REQUIRED_FILES.rst,\
./Help/variable/CTEST_COVERAGE_COMMAND.rst,\
./Modules/CMakeCheckCompilerFlagCommonPatterns.cmake,\
./Modules/CMakeRCInformation.cmake,\
./Modules/Internal/CPack/NSIS.template.in,\
./Modules/FindMatlab.cmake,\
./Modules/MatlabTestsRedirect.cmake,\
./Modules/Platform/Windows-Clang.cmake,\
./Modules/Platform/Windows-Intel-Fortran.cmake,\
./Modules/Platform/Windows-MSVC.cmake,\
./Source/CMakeVersion.cmake,\
./Source/cmConvertMSBuildXMLToJSON.py,\
./Source/cmCreateTestSourceList.cxx,\
./Source/cmGlobalVisualStudio10Generator.cxx,\
./Source/cmExportBuildFileGenerator.cxx,\
./Source/cmExportInstallAndroidMKGenerator.cxx,\
./Source/cmExportInstallFileGenerator.cxx,\
./Source/cmExportSet.cxx,\
./Source/cmExportTryCompileFileGenerator.cxx,\
./Source/cmFindPackageCommand.cxx,\
./Source/cmInstallCommand.cxx,\
./Source/cmGeneratorExpressionLexer.cxx,\
./Source/cmLocalVisualStudio7Generator.cxx,\
./Source/cmOrderDirectories.cxx,\
./Source/cmTarget.cxx,\
./Source/kwsys/*,\
./Source/QtDialog/CMakeSetupDialog.ui,\
./Source/CPack/WiX/cmWIXRichTextFormatWriter.cxx,\
./Source/CTest/cmParseCoberturaCoverage.h,\
./Tests/CMakeTests/ImplicitLinkInfoTest.cmake.in,\
./Tests/RunCMake/CPack/tests/DMG_SLA/English.license.rtf,\
./Tests/RunCMake/CPack/tests/DMG_SLA/German.license.txt,\
./Tests/RunCMake/CPack/tests/DMG_SLA/German.menu.txt,\
./Tests/RunCMake/GoogleTest/xml_output.cpp,\
./Tests/RunCMake/Make/TargetMessages*,\
./Utilities/*,\
" \
-L "\
dependees,\
endwhile,\
fo,\
filetest,\
helpfull,\
nd,\
objext,\
stoll,\
supercedes,\
superceded,\
vas,\
varn,\
"
```

1 files changed, 2 insertions, 2 deletions

diff --git a/Modules/CMakeParseImplicitIncludeInfo.cmake b/Modules/CMakeParseImplicitIncludeInfo.cmake
index ff4c325..7cd7548 100644
--- a/Modules/CMakeParseImplicitIncludeInfo.cmake
+++ b/Modules/CMakeParseImplicitIncludeInfo.cmake
@@ -7,7 +7,7 @@
 # for compilers that report them that way.  on success we return the
 # list of dirs in id_var and set state_var to the 'done' state.
 function(cmake_parse_implicit_include_line line lang id_var log_var state_var)
-  # clear variables we append to (avoids possible polution from parent scopes)
+  # clear variables we append to (avoids possible pollution from parent scopes)
   unset(rv)
   set(log "")
 
@@ -162,7 +162,7 @@ endfunction()
 function(cmake_parse_implicit_include_info text lang dir_var log_var state_var)
   set(state start)    # values: start, loading, done
 
-  # clear variables we append to (avoids possible polution from parent scopes)
+  # clear variables we append to (avoids possible pollution from parent scopes)
   set(implicit_dirs_tmp)
   set(log "")