userspace/libsinsp/parsers: fix compiler error on Windows

Provide a fallback implementation of memmem, which is a GNU extension
userspace/libsinsp: move fallback memmem into the right file
userspace/libsinsp: use a cleaner algorithm for fallback memmem
userspace/libsinsp/memmem: change code
Merge branch 'master' into filter-binary-buffer

Conflicts:
	userspace/libsinsp/parsers.h
Merge pull request #95 from ret2libc/filter-binary-buffer

userspace/libsinsp/parsers: fix compiler error on Windows