Skipping spaces in configuration files (ticket #1557). Previously, a chunk of spaces larger than NGX_CONF_BUFFER (4096 bytes) resulted in the "too long parameter" error during parsing such a configuration. This was because the code only set start and start_line on non-whitespace characters, and hence adjacent whitespace characters were preserved when reading additional data from the configuration file. Fix is to always move start and start_line if the last character was a space.