GBytes: add range-checked pointer getter

Closes #1098
10 jobs for range-checked in 18 minutes and 8 seconds (queued for 1 second)
Status Job ID Name Coverage
  Style Check
passed #1341377
check-todos

00:00:56

failed #1341376
allowed to fail
style-check-diff

00:01:01

 
  Build
passed #1341380
cross-android_api21_arm64

00:01:42

passed #1341381
cross-android_api28_arm64

00:01:54

passed #1341382
cross-mingw64

00:02:14

passed #1341379
debian-stable-x86_64

00:03:42

passed #1341378
fedora-x86_64

00:08:41

passed #1341383
win32-ps
msys2-mingw32

00:14:57

passed #1341384
win32-ps
vs2017-x64

00:08:47

 
  Coverage
passed #1341385
coverage

00:00:44

76.2%
 
Name Stage Failure
failed
style-check-diff Style Check
+gconstpointer g_bytes_get_region (GBytes *bytes,
+ gsize element_size,
+ gsize offset,
+ gsize n_elements);

G_END_DECLS

Cleaning up file based variables
ERROR: Job failed: exit code 1