windows build: ignore generated files (nmake)
(cherry picked from commit 23f33ca20ec563f5484ae71c05cf1eb1965410c4)
windows build: use different .def file for xp

Use different def file for windows < 5.1.
(cherry picked from commit 57d295441fb2d7d1cb4264ab57aa244799b9198f)
ios build: fixed toolchain for cmake 2.8.10
(cherry picked from commit 7b706ba8400bd07de3bda66a1d865168f2081495)
ios simulator build: set CMAKE_OSX_SYSROOT

When building for iphone simulator it is required to set the CMAKE_OSX_SYSROOT
to "iphonesimulator" otherwise command line builds (with cmake --build) will fail.
(cherry picked from commit 6d2142182dc7c450286b63bdfc579855951796d7)
ios build: added option to set signing certificate

Code signing certificate can be set with with cmake option CODE_SIGN_IDENTITY.
Like -DCODE_SIGN_IDENTITY="signing identity"
(cherry picked from commit f30d3ac3a123c13f8acb11323b432a6855d52668)
Cleaned up and improved iOS openssl build script

* Added support for optional build directory (first argument)
* Automatically detect iOS/iPhoneSimulator SDKs (oldest SDK found is used)
(cherry picked from commit e30d6109bca5c1dd202656716203fec0525f40a0)
ios ssl build: do sdk detection before download
(cherry picked from commit 27d8844fab091d36a673b92c1152cdb991ef2d02)
ios ssl build: support for user specified sdks

To build against a specific (not auto detected) SDK version set
USER_OS_SDK and/or USER_SIM_SDK at the top of the script.
(cherry picked from commit 38883e5ecdd616d7a6ff04bc2f5861a34a6c9851)
ios build: updated README.ios
(cherry picked from commit fa1bc1f2feed1fefee6ef935025e9ec6da523efc)