module_mapper_t causes docs to fail to build with doxygen 1.8.1

On my Windows machine module_mapper_t from 91a632de #3129 (closed) breaks the build:

FAILED: cmd.exe /C "cd /D D:\derek\dr\git\build_x64_dbg_tests\api\docs && C:\PROGRA~2\CMake\bin\cmake.exe -D DOXYGEN_EXECUTABLE=C:/cygwin64/usr/local/bin/doxygen.exe -Ddoxygen_ver=1.8.1.1 -Dversion_number=7.0.17764 "-Dmodule_string_long=\"DynamoRIO Extension Details\"" -Dmodule_string_short=\"Extension\" -Dhome_url=\"http://www.dynamorio.org\" "-Dhome_title=\"DynamoRIO Home Page\"" -Dlogo_imgfile=\"drlogo.png\" -P D:/derek/dr/git/src/api/docs/CMake_rundoxygen.cmake"
CMake Error at D:/derek/dr/git/src/api/docs/CMake_rundoxygen.cmake:143 (message):
  *** C:/cygwin64/usr/local/bin/doxygen.exe failed: ***

  D:/derek/dr/git/src/api/docs/release.dox:227: warning: explicit link
  request to 'module_mapper_t' could not be resolved

  deprecated:47: warning: explicit link request to 'module_mapper_t' could
  not be resolved

  deprecated:49: warning: explicit link request to
  'module_mapper_t::get_loaded_modules()' could not be resolved

  deprecated:51: warning: explicit link request to
  'module_mapper_t::find_mapped_trace_address()' could not be resolved


  D:/derek/dr/git/build_x64_dbg_tests/clients/include/drmemtrace/raw2trace.h:247:
  warning: explicit link request to 'module_mapper_t' could not be resolved


  D:/derek/dr/git/build_x64_dbg_tests/clients/include/drmemtrace/raw2trace.h:263:
  warning: explicit link request to 'module_mapper_t::get_loaded_modules()'
  could not be resolved


  D:/derek/dr/git/build_x64_dbg_tests/clients/include/drmemtrace/raw2trace.h:277:
  warning: explicit link request to
  'module_mapper_t::find_mapped_trace_address()' could not be resolved

ninja: build stopped: subcommand failed.

Is it the keyword "final" in "class module_mapper_t final"? This is doxygen 1.8.1.1. cygwin doxgyen 1.8.14 seems to work. Linux has no trouble: 1.8.13 for me, not sure what Travis has.

On Appveyor: it looks like the winfig zip URL is messed up, but the docs were already disabled there due to ghostscript issues (#2145 (closed)).

cc @mtrofin