This should fix Stan's USE_POSIX_SIGNALS problem as well

src/makefiles/Makefile.hpux

@@ -2,7 +2,6 @@ HPUX_MAJOR= $(shell uname -r|sed 's/^[^.]*\.\([^.]*\).*/\1/')
 # HP-UX 10 has a select() in libcurses, so we need to get the libc version first
 ifeq ($(HPUX_MAJOR), 10)
    LDFLAGS:= -Wl,-E -lc $(LDFLAGS)
-   CFLAGS+= -DUSE_POSIX_SIGNALS
 endif
 
 # HP-UX 09 needs libc before libPW, so we need to get the libc version first