remove MAX_HEADER_NAME_LENGTH from header

Still lurking aound as a ghost after all real usess of it
were removed with the minilex changes.

Signed-off-by: Andy Green <andy.green@linaro.org>
move ssl cipher list from compiletime to context creation time option

More flexible this way... NULL for the new member means use
the ssl library default set of ciphers, so as long as your info
struct is zerod by bss or memset, you don't need to do anything
about this change unless you want to set the cipher list.

Signed-off-by: Andy Green <andy.green@linaro.org>