tool_paramhlp: Fixed compilation warnings

declaration of 'index' shadows a global declaration
easy: Fixed a memory leak on OOM condition
stunnel: regenerated self-signed test certificate with SHA1 hash

The previous test certificate contained a MD5 hash which is not
supported using TLSv1.2 with Schannel on Windows 7 or newer.

See the update to this blog post on IEInternals / MSDN:
http://blogs.msdn.com/b/ieinternals/archive/2011/03/25/
misbehaving-https-servers-impair-tls-1.1-and-tls-1.2.aspx

"Update: If the server negotiates a TLS1.2 connection with a
Windows 7 or 8 schannel.dll-using client application, and it
provides a certificate chain which uses the (weak) MD5 hash
algorithm, the client will abort the connection (TCP/IP FIN)
upon receipt of the certificate."
RELEASE-NOTES: added note about impact of changes to WinSSL defaults
tool_operate: Moved list engines into separate function in tool_help
tool_operhlp: Consolidated engine output code into tool_help
tool_operhlp.h: Fixed compilation warning

warning: 'struct Configurable' declared inside parameter list
tool_getparam: Moved version information into separate function in tool_help
tool: Fixed incorrect return code when setting HTTP request fails

During initialisation SetHTTPrequest() may fail and cURL would return
PARAM_BAD_USE, which is equivalent to CURLE_NOT_BUILT_IN in cURL error
terms.

Instead, return CURLE_FAILED_INIT as we do for other functions that may
fail during initialisation.
tool_operate: Start to use CURLcode rather than int for return codes

To help assist with the detection of incorrect return codes, as per
commits ee23d13a79, 33b8960dc8 and aba98991a5, updated the operate
based functions to return CURLcode error codes.
tool_cfgable: Removed list_engine flag from config structure

In preparation for separating the global config options from the per
operation config options, reworked the list engines code to not use a
member variable in the Configurable structure.
tool_getparam: Moved tool_version_info() call into operate()
tool_getparam: Moved hugehelp() call into operate()
tool_getparam: Moved tool_help() call into operate()
RELEASE-NOTES: Synced with 8c80840d01
tool: Fixed incorrect return code with --version from commit c10bf9bb36
tool_cfgable: Renamed Configurable structure to OperationConfig

To allow for the addition of a global config structure and prevent
confusion between the two.
tool_cfgable: Added global config structure
tool_main: Moved initial OperateConfig creation into main_init()
tool_main: Moved OperateConfig cleanup into main_free()