(EMPTH_LWP, EMPTH_POSIX, EMPTH_W32): Define in config.h instead of

compiler command line.  Don't bother to conditionalize code in .c
files that are only compiled when their thread package is used.

(_EMPTH_LWP, EMPTH_LWP, _EMPTH_POSIX, EMPTH_POSIX, _EMPTH_WIN32)
(EMPTH_W32): Identifiers beginning with an underscore and an uppercase
letter are reserved for any use.  Rename.

src/lib/lwp/sel.c

@@ -44,8 +44,6 @@
 #include "lwp.h"
 #include "lwpint.h"
 
-#if defined(_EMPTH_LWP)
-
 struct lwpSelect {
     int maxfd;
     int nfds;
@@ -228,4 +226,3 @@ lwpSelect(void *arg)
     }
     /*NOTREACHED*/
 }
-#endif