doxygen (2015Q4) can't grok 'flex' version on i386-7.99.26

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

Building "devel/doxygen" frpm pkgsrc-2015Q4 on:

NetBSD verthandi 7.99.26 NetBSD 7.99.26 (VERTHANDI) #1: Fri Feb 12 22:16:21 CST 2016  sysop%verthandi.technoskunk.fur@localhost:/d0/build/nbsd-tst/obj/i386/sys/arch/i386/compile/VERTHANDI i386

fails with:

[...]
/d0/build/pkgsrc/devel/doxygen/work/.tools/bin/flex -i -PvhdlcodeYY -t vhdlcode.l | /usr/pkg/bin/python2.7 increasebuffer.py > ../generated_src/doxygen/vhdlcode.cpp
g++ -c -Wall -W -O2  -I/usr/include -I/usr/pkg/include -I/usr/pkg/include/freetype2 -I../generated_src/doxygen -I../src -I../qtools -I../libmd5 -I../vhdlparser -o ../objects/doxygen/vhdlcode.o ../generated_src/doxygen/vhdlcode.cpp
vhdlcode.l:1618:2: error: #error "You seem to be using a version of flex newer than 2.5.4 but older than 2.5.33. These versions do NOT work with doxygen! Please use version <=2.5.4 or >=2.5.33 or expect things to be parsed wrongly!"
 #endif
  ^
Makefile.libdoxygen:4527: recipe for target '../objects/doxygen/vhdlcode.o' failed
gmake[2]: *** [../objects/doxygen/vhdlcode.o] Error 1
gmake[2]: Leaving directory '/d0/build/pkgsrc/devel/doxygen/work/doxygen-1.8.9.1/src'
Makefile:41: recipe for target 'all' failed
gmake[1]: *** [all] Error 2
gmake[1]: Leaving directory '/d0/build/pkgsrc/devel/doxygen/work/doxygen-1.8.9.1/src'
Makefile:24: recipe for target 'all' failed
gmake: *** [all] Error 2
*** Error code 2

Stop.
make[3]: stopped in /x/pkgsrc/devel/doxygen
*** Error code 1

Stop.
[...]


$ which -a flex
/usr/bin/flex

$ flex --version
flex 2.6.0

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