OpenSystemsDevelopment / qpdf

* Return rather than exiting from realmain in qpdf.cc
* Remove extraneous blank line
* Don't assign temporary to const reference

The jpeg library has some assembly code that is missed by the compiler
instrumentation used by memory sanitization. There is a runtime
environment variable that is used to work around this issue.

Specifically, if a stream had its stream data replaced and had
indirect /Filter or /DecodeParms, it would result in non-silent loss
of data and/or internal error.

Fixes a crash found by fuzzing.

OPENSSL_IS_BORINGSSL is not actually set by configure, so it will be
undefined until a BoringSSL header is included.  Hence the #ifdef logic
in QPDFCrypto_openssl.h would usually never apply.

This still worked because evp.h transitively included BoringSSL's
cipher.h and digest.h, but the latter are the correct (documented)
headers.

By re-ordering the includes, we can ensure the macro is defined when we
use it.

Also: fix case in the header guards.

Fixes qpdf/qpdf#450

On large files with predominantly \n line endings, memchr(..'\r'..)
seems to waste a considerable amount of time searching for a line
ending candidate that we don't need.

On the Adobe PDF Reference Manual 1.7, this commit is 8x faster at
QPDF::processMemoryFile().

Use autoconf rather than ifdefs to determine what format string to use
for long long.

When possible, use `for (auto&` or `for (auto const&` when iterating
using C++-11 style iterators.

Also switch to colon-style iteration in some cases. Thanks to Dean
Scarff for drawing this to my attention after detecting some
unnecessary copies with
https://clang.llvm.org/extra/clang-tidy/checks/performance-for-range-copy.html

This uses C++-11 thread-safe static initializers now.

Fixes qpdf/qpdf#417

StreamDataProvider::provideStreamData now has a rich enough API for it
to effectively proxy to pipeStreamData.

Fixes qpdf/qpdf#419

This was being saved until we had to break ABI.

This was added in C++11.