gtype: suppress valgrind memory leak warningsmcatanzaro/#2076

The problem occurs because we keep a pointer inside the allocated block,
instead of a pointer to the start of the block. This memory exists for
the lifetime of the application, so let's silence it.

This is probably abuse of VALGRIND_MALLOCLIKE_BLOCK(), which is really
intended for use in memory allocators, but gtype.c already uses it in
two other places, and it's a practical solution. I wrote another larger
fix for this issue that involves keeping an array of extra pointers when
running under valgrind. This is simpler.

Fix suggested by Philip Withnall

```
==180238== 16 bytes in 1 blocks are possibly lost in loss record 3,078 of 16,075
==180238==    at 0x483BB1A: calloc (vg_replace_malloc.c:762)
==180238==    by 0x5489495: g_malloc0 (gmem.c:132)
==180238==    by 0x5489754: g_malloc0_n (gmem.c:364)
==180238==    by 0x53FDBEE: type_set_qdata_W (gtype.c:3722)
==180238==    by 0x53FDEE8: type_add_flags_W (gtype.c:3787)
==180238==    by 0x53FC348: g_type_register_fundamental (gtype.c:2662)
==180238==    by 0x53D969B: _g_enum_types_init (genums.c:124)
==180238==    by 0x53FF058: gobject_init (gtype.c:4432)
==180238==    by 0x53FF082: gobject_init_ctor (gtype.c:4493)
==180238==    by 0x4010F29: call_init.part.0 (dl-init.c:72)
==180238==    by 0x4011030: call_init (dl-init.c:30)
==180238==    by 0x4011030: _dl_init (dl-init.c:119)
==180238==    by 0x4002149: ??? (in /usr/lib64/ld-2.30.so)
```

Fixes #2076

1 files changed, 1 insertions, 0 deletions

diff --git a/gobject/gtype.c b/gobject/gtype.c
index 909faf138..26c7a0e11 100644
--- a/gobject/gtype.c
+++ b/gobject/gtype.c
@@ -440,6 +440,7 @@ type_node_any_new_W (TypeNode             *pnode,
   if (!pnode)					      /* offset fundamental types */
     {
       node = G_STRUCT_MEMBER_P (node, SIZEOF_FUNDAMENTAL_INFO);
+      VALGRIND_MALLOCLIKE_BLOCK (node, node_size - SIZEOF_FUNDAMENTAL_INFO, FALSE, TRUE);
       static_fundamental_type_nodes[ftype >> G_TYPE_FUNDAMENTAL_SHIFT] = node;
       type = ftype;
     }