Without this function declaration, the build fails on modern C compilers (ISO C99). This affects e.g. builds on Apple Silicon. This fix is also needed in order to compile rasspy/piper on Apple silicon

When looking for dotted abbreviations we must limit ourself to the size of
the buffer used for translating the abbreviation.

As reported in <https://bugs.freebsd.org/271486>, when the C++ standard
library provides std::sample, it causes a compile error when compiling
speechWaveGenerator.cpp:

  src/speechPlayer/src/speechWaveGenerator.cpp:197:56: error: reference to 'sample' is ambiguous
          unsigned int generate(const unsigned int sampleCount, sample* sampleBuf) {
                                                                ^
  src/speechPlayer/src/sample.h:23:3: note: candidate found by name lookup is 'sample'
  } sample;
    ^
  /usr/include/c++/v1/__algorithm/sample.h:95:17: note: candidate found by name lookup is 'std::sample'
  _SampleIterator sample(_PopulationIterator __first,
                  ^

Since speechWaveGenerator.cpp puts "using namespace std;" at the top,
fix the error by qualifying "sample" with an explicit "::".

Fixes #1660.