Previous interfaces for these libcurl internal functions did not allow to tell
apart a legitimate zero size result from an error condition. These functions
now return a CURLcode indicating function success or otherwise specific error.
Output size is returned using a pointer argument.

All usage of these two functions, and others closely related, has been adapted
to the new interfaces. Relative error and OOM handling adapted or added where
missing. Unit test 1302 also adapted.

Fix compiler warning: conversion may lose significant bits

Fix compiler warning: variable was set but never used

Fix compiler warning: clobber ignored

That's the symbol we have or generate in include/curl/curlbuild.h

This commit fixes the cmake build of curl, and cleans up the
cmake code a little.  It removes some commented out code and
some trailing whitespace.  To get curl to build the binary
tree include/curl directory needed to be added to the include
path. Also, SIZEOF_SHORT needed to be added.  A check for the
lack of defines of SIZEOF_* for warnless.c was added.

Added SIZEOF_INT and SIZEOF_SHORT definitions for non-configure systems

fix compiler warning

convert Curl_ultous() and Curl_ultouc() functions to curlx_ultous() and
curlx_ultouc(), exposing them through curlx.h to allow proper code reuse
later in our test harness.

fix compiler warning

fix compiler warning

removed trailing whitespace

in libcurl as well, if necessary.