CLEANUP: build: rename some build macros to use the USE_* ones

We still have quite a number of build macros which are mapped 1:1 to a
USE_something setting in the makefile but which have a different name.
This patch cleans this up by renaming them to use the USE_something
one, allowing to clean up the makefile and make it more obvious when
reading the code what build option needs to be added.

The following renames were done :

 ENABLE_POLL -> USE_POLL
 ENABLE_EPOLL -> USE_EPOLL
 ENABLE_KQUEUE -> USE_KQUEUE
 ENABLE_EVPORTS -> USE_EVPORTS
 TPROXY -> USE_TPROXY
 NETFILTER -> USE_NETFILTER
 NEED_CRYPT_H -> USE_CRYPT_H
 CONFIG_HAP_CRYPT -> USE_LIBCRYPT
 CONFIG_HAP_NS -> DUSE_NS
 CONFIG_HAP_LINUX_SPLICE -> USE_LINUX_SPLICE
 CONFIG_HAP_LINUX_TPROXY -> USE_LINUX_TPROXY
 CONFIG_HAP_LINUX_VSYSCALL -> USE_LINUX_VSYSCALL
diff --git a/include/common/splice.h b/include/common/splice.h
index ea29b16..760b6ba 100644
--- a/include/common/splice.h
+++ b/include/common/splice.h
@@ -23,7 +23,7 @@
 #ifndef _COMMON_SPLICE_H
 #define _COMMON_SPLICE_H
 
-#if defined (__linux__) && defined(CONFIG_HAP_LINUX_SPLICE)
+#if defined (__linux__) && defined(USE_LINUX_SPLICE)
 
 #include <errno.h>
 #include <unistd.h>
@@ -49,7 +49,7 @@
 
 #if defined(USE_MY_SPLICE)
 
-#if defined(CONFIG_HAP_LINUX_VSYSCALL) && defined(__linux__) && defined(__i386__)
+#if defined(USE_LINUX_VSYSCALL) && defined(__linux__) && defined(__i386__)
 /* The syscall is redefined somewhere else */
 extern int splice(int fdin, loff_t *off_in, int fdout, loff_t *off_out, size_t len, unsigned long flags);
 #else
@@ -71,7 +71,7 @@
 
 #endif /* USE_MY_SPLICE */
 
-#endif /* __linux__ && CONFIG_HAP_LINUX_SPLICE */
+#endif /* __linux__ && USE_LINUX_SPLICE */
 
 #endif /* _COMMON_SPLICE_H */