Declare lwlock.c's LWLockAcquireCommon() as a static inline.

68a2e52b has introduced LWLockAcquireCommon() containing the
previous contents of LWLockAcquire() plus added functionality. The
latter then calls it, just like LWLockAcquireWithVar(). Because the
majority of callers don't need the added functionality, declare the
common code as inline. The compiler then can optimize away the unused
code. Doing so is also useful when looking at profiles, to
differentiate the users.

Backpatch to 9.4, the first branch to contain LWLockAcquireCommon().

src/backend/storage/lmgr/lwlock.c

@@ -85,8 +85,8 @@ static LWLock *held_lwlocks[MAX_SIMUL_LWLOCKS];
 static int	lock_addin_request = 0;
 static bool lock_addin_request_allowed = true;
 
-static bool LWLockAcquireCommon(LWLock *l, LWLockMode mode, uint64 *valptr,
-					uint64 val);
+static inline bool LWLockAcquireCommon(LWLock *l, LWLockMode mode,
+					uint64 *valptr, uint64 val);
 
 #ifdef LWLOCK_STATS
 typedef struct lwlock_stats_key
@@ -510,7 +510,7 @@ LWLockAcquireWithVar(LWLock *l, uint64 *valptr, uint64 val)
 }
 
 /* internal function to implement LWLockAcquire and LWLockAcquireWithVar */
-static bool
+static inline bool
 LWLockAcquireCommon(LWLock *l, LWLockMode mode, uint64 *valptr, uint64 val)
 {
 	volatile LWLock *lock = l;