pgsql: Add pg_strnlen() a portable implementation of strlen.

Applying: Rewrite strnlen replacement implementation from 8a241792f96.
Using index info to reconstruct a base tree...
M	configure
A	configure.in
M	src/backend/utils/mmgr/mcxt.c
M	src/common/string.c
M	src/include/common/string.h
M	src/include/pg_config.h.in
A	src/include/pg_config.h.win32
M	src/include/port.h
M	src/port/snprintf.c
Falling back to patching base and 3-way merge...
Auto-merging src/port/snprintf.c
CONFLICT (content): Merge conflict in src/port/snprintf.c
Auto-merging src/include/port.h
CONFLICT (content): Merge conflict in src/include/port.h
CONFLICT (modify/delete): src/include/pg_config.h.win32 deleted in HEAD and modified in Rewrite strnlen replacement implementation from 8a241792f96.. Version Rewrite strnlen replacement implementation from 8a241792f96. of src/include/pg_config.h.win32 left in tree.
Auto-merging src/include/pg_config.h.in
CONFLICT (content): Merge conflict in src/include/pg_config.h.in
Auto-merging src/include/common/string.h
CONFLICT (content): Merge conflict in src/include/common/string.h
Auto-merging src/common/string.c
CONFLICT (content): Merge conflict in src/common/string.c
Auto-merging src/backend/utils/mmgr/mcxt.c
CONFLICT (content): Merge conflict in src/backend/utils/mmgr/mcxt.c
Auto-merging configure.ac
CONFLICT (content): Merge conflict in configure.ac
Auto-merging configure
CONFLICT (content): Merge conflict in configure
Patch failed at 0001 Rewrite strnlen replacement implementation from 8a241792f96.

error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"