This is one of those little chores in managing a long-lived C++
project: standard C headers like stdio.h and math.h now have their own
place in the C++ standard as resp. cstdio, cmath, and so on. In this
branch the #include names are updated for the phrase-extract/
subdirectory; more branches to follow.
C++11 adds cstdint, but to support compilation with the previous
standard, that change is left for later.
