the curl_easy_strerror() function to provide one

defined (which it never is atm).

Now, we can focus on making 'runtests -t [num]' work on all test cases and
we should never leak nor crash.

accordingly

from 64 bit types to 32 bit ones

curlx_-functions with the new prefix to prepare this code for the future
removal of several curl_-functions from the public libcurl API.

the correct config.h for the platform, and when this is done the USE_MANUAL
define is properly known.

in alphabetical order

will be properly built with configure --disable-manual even if the source
file is already present

concept, and added lib/README.curlx to explain details about it

such platforms that support large files.