http.c: fix compiling with libcurl 7.9.2

Change the minimimum required libcurl version for the http.sslKey option
to 7.9.3.  Previously, preprocessor macros checked for >= 7.9.2, which
is incorrect because CURLOPT_SSLKEY was introduced in 7.9.3.  This now
allows git to compile with libcurl 7.9.2.

Signed-off-by: Mark Lodato <lodatom@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http.c

@@ -14,7 +14,7 @@ char curl_errorstr[CURL_ERROR_SIZE];
 
 static int curl_ssl_verify = -1;
 static const char *ssl_cert;
-#if LIBCURL_VERSION_NUM >= 0x070902
+#if LIBCURL_VERSION_NUM >= 0x070903
 static const char *ssl_key;
 #endif
 #if LIBCURL_VERSION_NUM >= 0x070908
@@ -119,7 +119,7 @@ static int http_options(const char *var, const char *value, void *cb)
 	}
 	if (!strcmp("http.sslcert", var))
 		return git_config_string(&ssl_cert, var, value);
-#if LIBCURL_VERSION_NUM >= 0x070902
+#if LIBCURL_VERSION_NUM >= 0x070903
 	if (!strcmp("http.sslkey", var))
 		return git_config_string(&ssl_key, var, value);
 #endif
@@ -189,7 +189,7 @@ static CURL *get_curl_handle(void)
 
 	if (ssl_cert != NULL)
 		curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
-#if LIBCURL_VERSION_NUM >= 0x070902
+#if LIBCURL_VERSION_NUM >= 0x070903
 	if (ssl_key != NULL)
 		curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
 #endif
@@ -303,7 +303,7 @@ void http_init(struct remote *remote)
 		curl_ssl_verify = 0;
 
 	set_from_env(&ssl_cert, "GIT_SSL_CERT");
-#if LIBCURL_VERSION_NUM >= 0x070902
+#if LIBCURL_VERSION_NUM >= 0x070903
 	set_from_env(&ssl_key, "GIT_SSL_KEY");
 #endif
 #if LIBCURL_VERSION_NUM >= 0x070908