remove 'sprint' helpers

remove 'sprint' helpers

Since these were added a year ago in 08786bbb19bbe0fdf28adcbb305b02f54a237edf,
they have only been used once in 6437e1535c7da1cb97fd215131c4bd92c60021fe in
code that was subsequently deleted in c2d3526427a7259aa656ab72c83b43232ebfd806.
At this point, it seems safe to call “time” on these and judge them as not
useful in practice.

To further reinforce this, it is worth observing that they were not usable in
the CMake build system. 5b620771b7e5f07529ff7a41177ae27048c91865, despite
correcting an absence of sprint.h, failed to also correct the absence of
sprint.c. Any attempt to use these functions resulted in link failures in the
CMake build.

This commit effectively reverts 5b620771b7e5f07529ff7a41177ae27048c91865 and
08786bbb19bbe0fdf28adcbb305b02f54a237edf.