Building audio/libtunepimp on Slackware Linux using the current
pkgsrc branch results in:

In file included from mp4.cpp:30:
/usr/pkgsrc/audio/libtunepimp/work/.buildlink/include/mp4.h:478:
error: `uint16_t' has not been declared

[...]

[wrapper.sh] note: The real command line, after the pkgsrc wrapper, was:
/usr/pkgsrc/audio/libtunepimp/work/.gcc/bin/g++ -DHAVE_CONFIG_H -I.
-I../.. -I../../include/tunepimp-0.5 -I../../libltdl
-I/usr/pkgsrc/audio/libtunepimp/work/.buildlink/include -Wall -O2 -O2
-march=athlon-xp -MT mp4.lo -MD -MP -MF .deps/mp4.Tpo -c mp4.cpp -fPIC
-DPIC -o .libs/mp4.o
-L/usr/pkgsrc/audio/libtunepimp/work/.buildlink/lib

[wrapper.sh] note: The real command line, after the pkgsrc wrapper, was:
/usr/pkg/bin/libtool --tag=CXX --mode=compile g++ -DHAVE_CONFIG_H -I.
-I../.. -I../../include/tunepimp-0.5 -I../../libltdl
-I/usr/pkgsrc/audio/libtunepimp/work/.buildlink/include -Wall -O2 -O2
-march=athlon-xp -MT mp4.lo -MD -MP -MF .deps/mp4.Tpo -c -o mp4.lo
mp4.cpp
*** Error code 1

Stop.