Speex-1.2.1

• Check for _WIN32 instead of WIN32 in preprocessor checks
• wav_io: check for EOF when seeking in wav (fixes hang discovered by fuzzing, see #9)
• CI: add gitlab CI integration
• fixed-point: make left shift macros use unsigned to avoid undefined behaviour
• math_approx: use unsigned int for LCG pseudorandom generator (avoids integer overflow)
• oss-fuzz: add integration and fuzzing target
• speexenc: guard against invalid channel numbers (see #13)
• speexdec: make left shift macros use unsigned to avoid undefined behaviour
• autotools: do not use deprecated macros

Thanks to Ralph Giles, Martin Storsjo, Luca Barbato, Michael Fink, Tyson Smith and orbea for your contributions.