allow *all* cstr method to use flash memory argumentsensure *all* cstr methods flow through same paths, avoid implicit String(cstr)throw out flashstringhelper method implementations in favour of cstr

consistent behaviour when accepting cstr input

expect empty cstr for simple methods, avoid doing it w/ length presentexpect {w,}buffer to be present, things are catastrophic anywaysalso, redundant wbuffer check for free()

introduce sys/ pgmspace.h, string.h and stdio.hconsistent signatures, avoid depending on newlib quirksallow strstr & strstr_P to be the same thing

wrappers expect length, thus no need to look for '\0'only missing piece is case-insensitive memcmp (memicmp?)since implementation requires it, manually do the tolower() loopupdate replace() w/o '\0' assumptions, always use mem rangesdrop strstr usage and reuse loop blocksalso returns actual len diff after comparison is otherwise equal

incorrectly using lastIndexOf, when should be using deduced search funcsince there is no reverse indexOf nor lastIndexOf allows end boundary,adjust buffer end pointer manually by swapping it w/ the found oneplus, reinit read ptr after possibly changing buffer() location

similar to replace() use, we already know there is nothing pastpreviously found needle ptr