Fix couple compiler warnings (#737)

* linux/bip6: Use function over PRINTF macro

Our repo should be C89 compatibale. C89 does not support variac macros.
For this reason use variac functions. This also enables to print
different streams than just stderr.

Also now if something is changed in debug_fprintf it also affect here
which is good.

* Use __inline__ over inline in library

Use __inline__ over inline as that is C89/C90 combatible. With MSVC we
need to use __inline so just define __inline__ to it if not already.

* h_get_alarm_sum: Fix -Wself-assign compiler warning

We get Wself-assign if PRINT_ENABLED is 0

```
src/bacnet/basic/service/h_get_alarm_sum.c:129:16:
  warning: explicitly assigning value of variable of type 'int' to itself
  [-Wself-assign]
[build]   129 |     bytes_sent = bytes_sent;
[build]       |     ~~~~~~~~~~ ^ ~~~~~~~~~~
```

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

src/bacnet/basic/service/h_get_alarm_sum.c

@@ -126,7 +126,7 @@ GET_ALARM_SUMMARY_ABORT:
         /*fprintf(stderr, "Failed to send PDU (%s)!\n", strerror(errno)); */
     }
 #else
-    bytes_sent = bytes_sent;
+    (void)bytes_sent;
 #endif
 
     return;

src/bacnet/basic/sys/platform.h

@@ -52,6 +52,9 @@
 #ifndef strncasecmp
 #define strncasecmp _strnicmp
 #endif
+#ifndef __inline__
+#define __inline__ __inline
+#endif
 #if (_MSC_VER < 1900)
 #include <stdio.h>
 #include <stdarg.h>

src/bacnet/basic/ucix/ucix.c

@@ -15,7 +15,7 @@
 
 static struct uci_ptr ptr;
 
-static inline int ucix_get_ptr(struct uci_context *ctx,
+static __inline__ int ucix_get_ptr(struct uci_context *ctx,
     const char *p,
     const char *s,
     const char *o,