Remove use of the inline keyword used as suggestion to compiler

Historically, the inline keyword was a strong suggestion to the compiler
that it should inline the function marked inline.  As compilers became
better at optimising, this functionality has receded, and using inline
as a suggestion to inline a function is obsolete.  The compiler will
happily ignore it and inline something else entirely if it finds that's
a better optimisation.

Therefore, remove all the occurences of the inline keyword with static
functions inside single compilation unit and leave the decision whether
to inline a function or not entirely on the compiler

NOTE: We keep the usage the inline keyword when the purpose is to change
the linkage behaviour.

doc/dev/style.md

@@ -269,7 +269,7 @@ specifying the implementation of the function.  The opening curly brace
 should occur on the same line as the argument list, unless the argument
 list is more than one line long:
 
-    	static inline void
+    	static void
     	func1(int i) {
     		/* whatever */
     	}