nss: ALPN and NPN support

Add ALPN and NPN support for NSS. This allows cURL to negotiate
HTTP/2.0 connections when built with NSS.
nss: support pre-ALPN versions
http2: updated README after NSS addition

Changed the support to a little matrix and added brief explanation of
what ALPN and NPN are for.
lib1515.c: Fixed various compilation warnings

lib1515.c:38:26 warning: unused parameter 'curl'
lib1515.c:38:81 warning: unused parameter 'ptr'
lib1515.c:38:5 warning: no previous prototype for 'debug_callback'
lib1515.c:46:5 warning: no previous prototype for 'do_one_request'
lib1515.c:120:3  warning: ISO C90 forbids mixed declarations and code

As well as some code policing such as white space and braces.
--help: add missing --tlsv1.x options
tool_cfgable: Introduced config_free() function
tool_cfgable: For consistency renamed init_config() to config_init()
runtests: Disable valgrind when debugging

This was already mostly being done, except that analysis after the
test still assumed that the valgrind log files would be available. An
alternative way to handle the valgrind + gdb combination could be to
enable one of the valgrind debugger hooks.
formdata: Fixed memory leak on OOM condition
secureserver: Disable FIPS mode for stunnel

It's unnecessary for curl testing, and it can otherwise cause
stunnel to fail to start if OpenSSL doesn't support FIPS mode.
tool_getparam: Added support for parsing of specific URL options
runtests: allow <strippart> to remove lines

For verify file, if the strippart condition removes the line completely
it is now removed from the array.
test96: updated according to recent changes
formdata: Must use Curl_safefree instead of free
tool_operate: Let curl handle cleanup take place in config_free()
tool_operate: Added support for performing URL specific operations
secureserver: FIPS option is only supported since stunnel 5.00
RELEASE-NOTES: Synced with 8e62f7a6503a
tests: Re-enabled IMAP tests that require URL specific option support
TODO: Removed url-specific options