... More to come, but needed some place to put PiotrSikora's handy little commands (and will expand on them later):

[edit] PiotrSikora

[edit] All Directives in Server context

find src/ -type f -name "*.c" -exec grep -B1 NGX_HTTP_SRV_CONF {} \; | grep ngx_string | cut -d\" -f2

[edit] All Variables in HTTP context

find src/ -type f -name "*.c" -exec grep -B2 NGX_HTTP_VAR {} \; | grep ngx_string | cut -d\" -f2