some LLVM function checks missing in meson

I have been checking the pg_config.h generated by configure and meson to
see if there is anything materially different. I found that

HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER and
HAVE_DECL_LLVMCREATEPERFJITEVENTLISTENER

are missing on the meson side.

Something like the below would appear to fix that:

diff --git a/meson.build b/meson.build
index 43fad5323c0..cdfd31377d1 100644
--- a/meson.build
+++ b/meson.build
@@ -2301,6 +2301,14 @@ decl_checks += [
['pwritev', 'sys/uio.h'],
]

+# Check presence of some optional LLVM functions.
+if llvm.found()
+ decl_checks += [
+ ['LLVMCreateGDBRegistrationListener', 'llvm-c/ExecutionEngine.h'],
+ ['LLVMCreatePerfJITEventListener', 'llvm-c/ExecutionEngine.h'],
+ ]
+endif
+
foreach c : decl_checks
func = c.get(0)
header = c.get(1)

I don't know what these functions do, but the symbols are used in the
source code. Thoughts?