Fix warnings in system/ headers

system/core/include is included in the global include path using
-isystem, which hides all warnings.  Fix warnings in
system/core/include/system in preparation for moving from -isystem to -I.

- Fix invalid doxygen syntax in graphics.h
- Use a pragma to hide a C99 extension warning on the flexible length
  array in graphics.h
- Make static functions in radio.h static inline
- Fix size_t printf and size_t vs. ssize_t comparision in qemu_pipe.h
- Fix old style cast in window.h

Test: m -j native
Bug: 31492149
Change-Id: I857f289e4c8e303494831873282bbb69de155c10
diff --git a/include/system/radio.h b/include/system/radio.h
index 9e291c8..d73d3ae 100644
--- a/include/system/radio.h
+++ b/include/system/radio.h
@@ -218,7 +218,8 @@
 } radio_event_t;
 
 
-static radio_rds_t radio_rds_for_region(bool rds, radio_region_t region) {
+static inline
+radio_rds_t radio_rds_for_region(bool rds, radio_region_t region) {
     if (!rds)
         return RADIO_RDS_NONE;
     switch(region) {
@@ -234,7 +235,8 @@
     }
 }
 
-static radio_deemphasis_t radio_demephasis_for_region(radio_region_t region) {
+static inline
+radio_deemphasis_t radio_demephasis_for_region(radio_region_t region) {
     switch(region) {
         case RADIO_REGION_KOREA:
         case RADIO_REGION_ITU_2: