basic clang compatibility on windows
build system to support clang
basic support for Intel Composer
fix x64 recognition for clang and icc
using the determined linker instead of compiler

this is a clang issue, longer parameter strings would be issue for both
compiler and linker
adjust pid_t declaration so it doesn't conflict with apache one
fix linking for clang, using linker directly
catch up the toolset changes with phpize

also packed common parts into functions so there's less code duplication
further refactoring of toolset+phpize stuff
parametrize WINVER and update its value
add /fallback for clang-cl
further catch up with phpize and improved clang arch setup
either ms or intel linker is used, /libpath is supported
fix gd compilation with icc toolset
rename intel toolset to icc - shorter
move more common ldflags into function