curl_getenv() is a portable wrapper for the getenv() function, meant to
emulate its behaviour and provide an identical interface for all operating
systems libcurl builds on (including win32).
AVAILABILITY
This function will be removed from the public libcurl API in a near future. It
will instead be made "available" by source code access only, and then as
curlx_getenv().
RETURN VALUE
If successful, curl_getenv() returns a pointer to the value of the specified
environment. The memory it refers to is malloc()ed so the application must
free() this when the data is no longer needed. When curl_getenv(3) fails
to find the specified name, it returns a null pointer.
NOTE
Under unix operating systems, there isn't any point in returning an allocated
memory, although other systems won't work properly if this isn't done. The
unix implementation thus have to suffer slightly from the drawbacks of other
systems.
