Use hMainProc where appropriate, throughout.

* environ.cc (spenv::retrieve): Add debugging statements.
* pinfo.cc (set_myself): Don't call strace.hello if already stracing.
* strace.cc (strace): Move NO_COPY keyword so that it will actually take
effect.

winsup/cygwin/strace.cc

@@ -22,7 +22,7 @@ details. */
 #define PROTECT(x) x[sizeof(x)-1] = 0
 #define CHECK(x) if (x[sizeof(x)-1] != 0) { small_printf("array bound exceeded %d\n", __LINE__); ExitProcess(1); }
 
-class NO_COPY strace strace;
+class strace NO_COPY strace;
 
 #ifndef NOSTRACE