add test coverage for _m variant functions

disallow NULL for cx_str() and cx_mutstr()

add tests and missing implementations for strings

implement strupper and strlower

implement more string functions

more implementations of string functions

start implementing string functions

some function can be macros using the default allocator

wrong position of struct identifier

first proposal for the string header

(0) -300 -100 -10 +10 +100 tip

mercurial