Fixed undefined symbol of getenv() which does not exist in WinRT.

[dmitrykos]

Fixed undefined symbol of getenv() which does not exist when compiling for Windows 10 App (CURL_WINDOWS_APP).

Replaced getenv() with curl_getenv() which is aware of getenv() absence when CURL_WINDOWS_APP is defined.

[bagder]

Thanks, but it seems your change doesn't follow our code style correctly:

./vtls/vtls.c:1286:2: error: Contains TAB character (TABS)
 		curl_free(env_tmp);
  ^

[dmitrykos]

Sorry, forgot to check for tabs! Removed them as advised.

[bagder]

Thanks!

[gvanem]

Replaced getenv() with curl_getenv() which is aware of getenv() absence when CURL_WINDOWS_APP
is defined.

What good does a curl_getenv() that always returns NULL for an UWP-app do? Does your app really work? According to MSDN, UWP-apps do have GetEnvironmentVariable(). No?

[dmitrykos]

What good does a curl_getenv() that always returns NULL for an UWP-app do? Does your app really work?

In this given context if curl_getenv("CURL_SSL_BACKEND") returns NULL then the first SSL backend is selected which is defined during a compile time in available_backends[0]. Should not be any problem at all.

Reference UWP app works correctly if curl_getenv() returns NULL, no problems observed within its scope of curl usage - HTTP(-S), FTP.

GetEnvironmentVariable would be useless for the Windows 10 Mobile platform as there is no way to set own environment variables if I am not mistaken.