[wmsdk][fix] Eliminate a pointless warning -

wm_os.h:229:13: warning: inline function 'os_enable_all_interrupts' declared but never defined [enabled by default]
wm_os.h:226:13: warning: inline function 'os_disable_all_interrupts' declared but never defined [enabled by default]
Merge pull request #72 from xively/fix_wmsdk_misc_warning

[wmsdk][fix] Eliminate a pointless warning -