examples on Windows: check for WSAStartup return code

Fixes VS2012 code analysis warning C6031:
return value ignored: <function> could return unexpected value
examples on Windows: check for socket return code

Fixes VS2012 code analysis warning C28193:
The variable holds a value that must be examined
agent.c: check return code of MapViewOfFile

Fixes VS2012 code analysis warning C6387: 'p+4' may be '0':
this does not adhere to the specification for the function
'memcpy': libssh2 agent.c 330

Fixes VS2012 code analysis warning C6387: 'p' may be '0':
this does not adhere to the specification for the function
'UnmapViewOfFile': libssh2 agent.c 333
kex.c: fix possible NULL pointer de-reference with session->kex

Fixes VS2012 code analysis warning C6011:
dereferencing NULL pointer 'session->kex'. libssh2 kex.c 1761
packet.c: fix possible NULL pointer de-reference within listen_state

Fixes VS2012 code analysis warning C6011:
dereferencing NULL pointer 'listen_state->channel'. libssh2 packet.c 221
wincng.c: fix possible use of uninitialized memory

Fixes VS2012 code analysis warning C6001:
using uninitialized memory 'cbDecoded'. libssh2 wincng.c 553
wincng.c: fix possible NULL pointer de-reference of bignum

Fixes VS2012 code analysis warning C6011:
dereferencing NULL pointer 'bignum'. libssh2 wincng.c 1567
tests on Windows: check for WSAStartup return code

Fixes VS2012 code analysis warning C6031:
return value ignored: <function> could return unexpected value
wincng.c: fix possible invalid memory write access

Fixes VS2012 code analysis warning C6386:
buffer overrun: accessing 'pbOutput', the writable size is
'cbOutput' bytes, but '3' bytes may be written: libssh2 wincng.c 610
wincng.c: explicitly ignore BCrypt*AlgorithmProvider return codes

Fixes VS2012 code analysis warning C6031:
return value ignored: <function> could return unexpected value
examples: fixed mixed line-endings introduced with aedfba25b8
x11 example: check return value of socket function
libssh2_priv.h: Ignore session, context and format parameters
CMake build working with Visual Studio 8.

Tested:
- static
- 32/64-bit
- OpenSSL/WinCNG
- Without zlib
Fix test for required crypto backend.
Fix case issue so examples build on Linux.
Let mansyntax.sh work regarless of where it is called from.
Invoke ssh2 test through wrapper that invokes sshd.
Mark test script executables as advanced.

The user usually will not want to set these manually.  They either have them or they don't.
Copy OpenSSL DLLs explicitly on Windows, rather than using fixup_bundle.

fixup_bundle was causing problems on Linux and didn't always find the right DLL on Windows.  It was also really slow on both platforms.

This commit just copies the two OpenSSL DLLs for each target that needs it.