Move MlirStringCallback declaration from mlir-c/IR.h to mlir-c/Support.h (NFC)

[mehdi_amini]

Summary

This is a generic utility that can be reused beyond the IR bindings.

[ftynse]

mlir/include/mlir-c/Support.h

53

Nit: reformat comment to C99

[mehdi_amini]

mlir/include/mlir-c/Support.h

53

I plan to do it separately for all the APIs in these headers.

mlir/include/mlir-c/IR.h

  * a string.
  */
 struct MlirNamedAttribute {
   const char *name;
   MlirAttribute attribute;
 };
 typedef struct MlirNamedAttribute MlirNamedAttribute;
 
-/** A callback for returning string references.
- *
- * This function is called back by the functions that need to return a reference
- * to the portion of the string with the following arguments:
- *   - a pointer to the beginning of a string;
- *   - the length of the string (the pointer may point to a larger buffer, not
- *     necessarily null-terminated);
- *   - a pointer to user data forwarded from the printing call.
- */
-typedef void (*MlirStringCallback)(const char *, intptr_t, void *);
-
 //===----------------------------------------------------------------------===//
 // Context API.
 //===----------------------------------------------------------------------===//
 
 /// Creates an MLIR context and transfers its ownership to the caller.
 MlirContext mlirContextCreate();
 
 /// Checks if two contexts are equal.

mlir/include/mlir-c/Support.h

inline MlirStringRef mlirStringRefCreate(const char *str, size_t length) {
   return result;
 }
 
 /** Constructs a string reference from a null-terminated C string. Prefer
  * mlirStringRefCreate if the length of the string is known.
  */
 MlirStringRef mlirStringRefCreateFromCString(const char *str);
 
+/** A callback for returning string references.
+ *
+ * This function is called back by the functions that need to return a reference
+ * to the portion of the string with the following arguments:
+ *   - a pointer to the beginning of a string;
+ *   - the length of the string (the pointer may point to a larger buffer, not
+ *     necessarily null-terminated);
+ *   - a pointer to user data forwarded from the printing call.
+ */
+typedef void (*MlirStringCallback)(const char *, intptr_t, void *);
+
 //===----------------------------------------------------------------------===//
 // MlirLogicalResult.
 //===----------------------------------------------------------------------===//
 
 /** A logical result value, essentially a boolean with named states. LLVM
  * convention for using boolean values to designate success or failure of an
  * operation is a moving target, so MLIR opted for an explicit class.
  * Instances of MlirLogicalResult must only be inspected using the associated