Fix compiler warning: variable was set but never used

Fix compiler warning: clobber ignored

Also define UNITTESTS macro when building unit test sources.

Fixing compiler warning: external definition with no prior declaration

When switching to HTTP because a HTTP proxy is being used, the existing
handler is now checked if it already is "compatible". This allows the https
handler remain while other non-http handlers will be redirected.

Bug: http://curl.haxx.se/mail/lib-2011-05/0214.html
Reported by: Jerome Robert

Fix compiler warning: variable was set but never used

Fix compiler warning: clobber ignored

Fix compiler warning: variable was set but never used

Fix compiler warning: clobber ignored

Fix compiler warning: external definition with no prior declaration

Fix compiler warning: external definition with no prior declaration

Fix compiler warning: argument is incompatible with corresponding format
string conversion

Enclose header file in an inclusion guard

Fix compiler warning: expression has no effect

Fix compiler warning: `keycheck' might be used uninitialized in this function.
Fix compiler warning: `keybit' might be used uninitialized in this function.

Fix variable declaration placement

Fix missing semicolon

Fix compiler warning: expression has no effect

Fix OOM handling

Fix compiler warning: expression has no effect

Fix compiler warning: unused variable 'data'

Fix compiler warning: enumerated type mixed with another type

Fix compiler warning: enumerated type mixed with another type

Fix compiler warning: enumerated type mixed with another type

Fix compiler warning: enumerated type mixed with another type

Fix compiler warning: enumerated type mixed with another type

Fix compiler warning: empty body in an if-statement

Additionally, prevent multiple inclusions of curl_config.h

winbuild: typo in docs

Get cyassl's NO_FILESYSTEM to work with libcurl. Otherwise I'd get linker
errors for the missing "SSL_CTX_load_verify_locations" functions.

Test 585: Fix opensocket return type, and avoid function name clash.

Fix linkage on c-ares enabled Windows static builds

Test 585 and 586 were added. Using a modified lib500.c

Fix the return type of the callback to match close() and make use of it.

Introduced the initial setup to allow closesocket callbacks by making
sure sclose() is only ever called from one place in the libcurl source
and still run all test cases fine.

Commit cbf4961b garbled the timeout handling while doing SSL
handshaking (in an attempt at fixing another bug). This puts sanity
back.

Bug: http://curl.haxx.se/mail/lib-2011-05/0167.html
Reported by: Ethan Glasser Camp