Support CURLOPT_ERRORBUFFER

[moteus]

Problems to solve

1. Where and when allocate error buffer.
   Options

• part of lcurl_easy_t structure
• full userdata and store ref/ptr to it internally
• new separate object lcurl_error_buffer_t and provide Lua API for it.

2. How to assign this option from Lua code (set to 0/1/true/false/nil/null)
3. Does it make sence allows to increase buffer size over than CURL_ERROR_SIZE? From the doc The buffer must be at least CURL_ERROR_SIZE bytes big.
4. Provide API for error object to access to information from associated buffer.