api-test-ws-h2-pmd: permessage-deflate over ws-over-h2 selftest

Single-process h2 ws server + client, both offering permessage-deflate,
ctest-wired like the other api-tests (needs LWS_WITHOUT_EXTENSIONS=OFF).
The server bulk-sends a 64KB deterministic pattern in 4KB messages gated
only on lws_send_pipe_choked(); alternate messages are trivially
compressible (deflated frame far smaller than the payload) and
incompressible hash noise (deflated output overflows pmd's default 1KB
chunk buffer, forcing tx_draining_ext).

It fails if the connection is not genuinely ws-over-h2, if the client's
extended CONNECT did not offer permessage-deflate, if any server
lws_write() reports fewer bytes accepted than requested, if the pattern
corrupts, or if the transfer stalls.

Against the pre-series code it catches all three fixes: without the
client extension offer it fails the handshake check; without the
orig_len return it fails immediately with 'short write: accepted 75 of
4096'; without the encapsulated tx_draining_ext servicing it wedges at
the first incompressible message (the POLLOUT mux loop hits its sanity
limit) and times out.

Author: thefallentree

minimal-examples-lowlevel/api-tests/api-test-ws-h2-pmd/CMakeLists.txt

@@ -0,0 +1,37 @@
+project(lws-api-test-ws-h2-pmd C)
+cmake_minimum_required(VERSION 3.10)
+find_package(libwebsockets CONFIG REQUIRED)
+list(APPEND CMAKE_MODULE_PATH ${LWS_CMAKE_DIR})
+include(CheckCSourceCompiles)
+include(LwsCheckRequirements)
+
+set(SAMP lws-api-test-ws-h2-pmd)
+set(SRCS main.c)
+
+set(requirements 1)
+require_lws_config(LWS_ROLE_WS 1 requirements)
+require_lws_config(LWS_ROLE_H2 1 requirements)
+require_lws_config(LWS_WITH_CLIENT 1 requirements)
+require_lws_config(LWS_WITH_SERVER 1 requirements)
+require_lws_config(LWS_WITH_TLS 1 requirements)
+require_lws_config(LWS_WITHOUT_EXTENSIONS 0 requirements)
+
+if (requirements)
+	add_executable(${SAMP} ${SRCS})
+
+	if (websockets_shared)
+		target_link_libraries(${SAMP} websockets_shared ${LIBWEBSOCKETS_DEP_LIBS})
+		add_dependencies(${SAMP} websockets_shared)
+	else()
+		target_link_libraries(${SAMP} websockets ${LIBWEBSOCKETS_DEP_LIBS})
+	endif()
+
+	lws_get_free_port(PORT_WS_H2_PMD)
+
+	add_test(NAME api-test-ws-h2-pmd COMMAND lws-api-test-ws-h2-pmd -p ${PORT_WS_H2_PMD})
+	set_tests_properties(api-test-ws-h2-pmd
+			     PROPERTIES
+			     WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/minimal-examples-lowlevel/api-tests/api-test-ws-h2-pmd
+			     TIMEOUT 60)
+
+endif()