winpr/pool: zero thread pool on creation
Merge pull request #926 from bmiklautz/zero_tp

winpr/pool: zero thread pool on creation
build: changed detection for i686/x86_64

Fixes compilation/feature detection on arm.
Merge pull request #929 from bmiklautz/armbuild

build: changed detection for i686/x86_64
added missing defined() in #elif

gcc >= 4.4 requires a condition in #elif.
Merge pull request #930 from bmiklautz/elif

added missing defined() in #elif
primitives: return value to fix compiler warning