[RELEASE] Released version 2.4-dev15

Released version 2.4-dev15 with the following main changes :
    - BUG/MINOR: payload: Wait for more data if buffer is empty in payload/payload_lv
    - BUG/MINOR: stats: Apply proper styles in HTML status page.
    - BUG/MEDIUM: time: make sure to always initialize the global tick
    - BUG/MINOR: tcp: fix silent-drop workaround for IPv6
    - BUILD: tcp: use IPPROTO_IPV6 instead of SOL_IPV6 on FreeBSD/MacOS
    - CLEANUP: socket: replace SOL_IP/IPV6/TCP with IPPROTO_IP/IPV6/TCP
    - BUG/MINOR: http_fetch: make hdr_ip() resistant to empty fields
    - BUG/MINOR: mux-h2: Don't emit log twice if an error occurred on the preface
    - MINOR: stream: Don't trigger errors on destructive HTTP upgrades
    - MINOR: frontend: Create HTTP txn for HTX streams
    - MINOR: stream: Be sure to set HTTP analysers when creating an HTX stream
    - BUG/MINOR: stream: Properly handle TCP>H1>H2 upgrades in http_wait_for_request
    - BUG/MINOR: config: Add warning for http-after-response rules in TCP mode
    - MINOR: muxes: Add a flag to notify a mux does not support any upgrade
    - MINOR: mux-h1: Don't perform implicit HTTP/2 upgrade if not supported by mux
    - MINOR: mux-pt: Don't perform implicit HTTP upgrade if not supported by mux
    - MEDIUM: mux-h1: Expose h1 in the list of supported mux protocols
    - MEDIUM: mux-pt: Expose passthrough in the list of supported mux protocols
    - MINOR: muxes: Show muxes flags when the mux list is displayed
    - DOC: config: Improve documentation about proto/check-proto keywords
    - MINOR: stream: Use stream type instead of proxy mode when appropriate
    - MINOR: filters/http-ana: Decide to filter HTTP headers in HTTP analysers
    - MINOR: http-ana: Simplify creation/destruction of HTTP transactions
    - MINOR: stream: Handle stream HTTP upgrade in a dedicated function
    - MEDIUM: Add tcp-request switch-mode action to perform HTTP upgrade
    - MINOR: config/proxy: Don't warn for HTTP rules in TCP if 'switch-mode http' set
    - MINOR: config/proxy: Warn if a TCP proxy without backend is upgradable to HTTP
    - DOC: config: Add documentation about TCP to HTTP upgrades
    - REGTESTS: Add script to tests TCP to HTTP upgrades
    - BUG/MINOR: payload/htx: Ingore L6 sample fetches for HTX streams/checks
    - MINOR: htx: Make internal.strm.is_htx an internal sample fetch
    - MINOR: action: Use a generic function to check validity of an action rule list
    - MINOR: payload/config: Warn if a L6 sample fetch is used from an HTTP proxy
    - MEDIUM: http-rules: Add wait-for-body action on request and response side
    - REGTESTS: Add script to tests the wait-for-body HTTP action
    - BUG/MINOR: http-fetch: Fix test on message state to capture the version
    - CLEANUP: vars: always pre-initialize smp in vars_parse_cli_get_var()
    - MINOR: global: define diagnostic mode of execution
    - MINOR: cfgparse: diag for multiple nbthread statements
    - MINOR: server: diag for 0 weight server
    - MINOR: diag: create cfgdiag module
    - MINOR: diag: diag if servers use the same cookie value
    - MINOR: config: diag if global section after non-global
    - TESTS: slightly reorganize the code in the tests/ directory
    - TESTS: move tests/*.cfg to tests/config
    - REGTESTS: ssl: "set ssl cert" and multi-certificates bundle
    - REGTESTS: ssl: mark set_ssl_cert_bundle.vtc as broken
    - CONTRIB: halog: fix issue with array of type char
    - CONTRIB: tcploop: add a shutr command
    - CONTRIB: debug: add the show-fd-to-flags script
    - CONTRIB: debug: split poll from flags
    - CONTRIB: move some dev-specific tools to dev/
    - BUILD: makefile: always build the flags utility
    - DEV: flags: replace the unneeded makefile with a README
    - BUILD: makefile: integrate the hpack tools
    - CONTRIB: merge ip6range with iprange
    - CONTRIB: move some admin-related sub-projects to admin/
    - CONTRIB: move halog to admin/
    - ADMIN: halog: automatically enable USE_MEMCHR on the right glibc version
    - BUILD: makefile: build halog with the correct flags
    - BUILD: makefile: add a "USE_PROMEX" variable to ease building prometheus-exporter
    - CONTRIB: move prometheus-exporter to addons/promex
    - DOC: add a few words about USE_* and the addons directory
    - CONTRIB: move 51Degrees to addons/51degrees
    - CONTRIB: move src/da.c and contrib/deviceatlas to addons/deviceatlas
    - CONTRIB: move src/wurfl.c and contrib/wurfl to addons/wurfl
    - CONTRIB: move contrib/opentracing to addons/ot
    - BUG/MINOR: opentracing: initialization after establishing daemon mode
    - DOC: clarify that compression works for HTTP/2
diff --git a/VERSION b/VERSION
index 87e9868..9142a54 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.4-dev14
+2.4-dev15