Maximum amount of data a header callback is supposed to get in
a single call from libcurl is limited by the lowest value of
CURL_MAX_WRITE_SIZE and CURL_MAX_HTTP_HEADER.

Allow (*curl_write_callback) write callbacks to return
CURL_WRITEFUNC_OUT_OF_MEMORY to properly indicate libcurl of OOM conditions
inside the callback itself.

When we use binary posts and regular ones intermixed on a single command
line, we cannot do strlen() etc on the data to figure out the length
(when inserting '&' and more). We must therefore keep track of the post
data length. Then we also end up setting the libcurl option with the
known size, so that we don't risk that libcurl will do strlen() on the
data.

This has the minor side-effect that --libcurl source codes now always
will use CURLOPT_POSTFIELDSIZE but I don't consider that terribly
damaging.

Bug: http://curl.haxx.se/bug/view.cgi?id=3413181
Reported by: Taneli Vähäkangas

my_setopt and my_setopt_str no longer ignores curl_easy_setopt result.

Fixed some OOM handling issues.

Related code not ready yet for this kind of checks.

Suffix rules cannot have any prerequisites of their own.

Added envvars to specify OpenSSL include, libpath and lib.
Added rule to create curlbuild.h from curlbuild.h.dist.

my_setopt and my_setopt_str no longer ignores curl_easy_setopt result.

Fixed some OOM handling issues.

Overhauled FindWin32CACert()

All paths to dependencies now quoted; synced examples makefile.

Additionally function my_useragent() now provides default User-Agent string

Reorder handling of fields to match same order as the one given by current
definition order of 'Configurable' struct fields. Fields currently not handled
marked for further inspection.

Reviewing fields being free'd in free_config_fields() still pending

Additionally some code reorganization and direct OOM handling fixes,
just another step towards fixing curl tool issues uncovered 2011-09-15

Additionally fix data type of result vars for iconv() calls

Re-enabling MemoryTracking capability on 'src' subdirectory files and torture
tests have uncovered many issues which were going unnoticed in curl tool. So
here we go fixing some of them. Others still remain and should be addressed
ASAP, given that curl tool is used in our test harness also for test server
start verification purposes. There are even non-socket file descriptor leaks.