implement "contains" function for strings
fixes
implemented substring search function: contains(haystack, needle)
extended logging
extended logging
working string "contains" operator
added str-two-way.h (substring search from gnulib)
moved str-two-way.h to correct location
contains(s1, s2) works without malloc and free, added tests
pep8 correction
reorg preprocessor directives
used str-two-way.h version from newlib that has permissive, BSD-like license
cleanup
Merging contains branch
Moved str-two-way.h  to .hpp to follow numexpr conventions
Fixed a typo.
Some code beautification for new contains tests
Added a simple test checking simple strings
Added the docs for new contains() function
Version bumped to 2.4.dev