Fix stackTrace() in preamble.js to support IE10 and IE11.
remove zlib headers from system/include
update csmith driver
document --memory-init-file on by default in opt builds in Changelog
Merge pull request #2544 from juj/stacktrace_js

IE stack trace fix.
testcase for #2539
add missing zconf.h in test suite
build enough of libcxxabi to support bad_typeid without undefined symbols; 1.21.5; fixes #2547
do not warn on malloc not present, we do so at runtime if used (+commented code to pull in malloc and other system libs based on EXPORTS)
update sanity.test_emcc_caching
move new.cpp from libc into libcxxabi
move isxdigit from libcextra to libc
DEMANGLE_SUPPORT option to use libcxxabi's demangler in stackTrace()
improve warning
fix looking up a file in a non-dir; fixes #2552
do not set EMCC_DEBUG=1 when -v; fixes #2538
Module.memoryInitializerPrefixURL option; #2542
make test_exceptions_white_list more robust
disable some exceptions tests in s_x_x