Fix wait loop and void cast (#24)

* Simplify EINTR/ECANCEL error handling

1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx

* Unify the void cast usage

1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro

binfmt/libnxflat/libnxflat_addrenv.c

@@ -169,7 +169,7 @@ int nxflat_addrenv_alloc(FAR struct nxflat_loadinfo_s *loadinfo, size_t envsize)
   return OK;
 
 errout_with_addrenv:
-  (void)up_addrenv_destroy(&loadinfo->addrenv);
+  up_addrenv_destroy(&loadinfo->addrenv);
   loadinfo->addrenv = 0;
 
 errout_with_dspace:

binfmt/libnxflat/libnxflat_bind.c

@@ -475,7 +475,7 @@ static inline int nxflat_bindimports(FAR struct nxflat_loadinfo_s *loadinfo,
             {
               berr("Exported symbol \"%s\" not found\n", symname);
 #ifdef CONFIG_ARCH_ADDRENV
-              (void)nxflat_addrenv_restore(loadinfo);
+              nxflat_addrenv_restore(loadinfo);
 #endif
               return -ENOENT;
             }

binfmt/libnxflat/libnxflat_load.c

@@ -215,9 +215,9 @@ int nxflat_load(struct nxflat_loadinfo_s *loadinfo)
 
 errout:
 #ifdef CONFIG_ARCH_ADDRENV
-  (void)nxflat_addrenv_restore(loadinfo);
+  nxflat_addrenv_restore(loadinfo);
 #endif
-  (void)nxflat_unload(loadinfo);
+  nxflat_unload(loadinfo);
   return ret;
 }