package/json-c: security bump to version 0.15

Fix CVE-2020-12762: json-c through 0.14 has an integer overflow and
out-of-bounds write via a large JSON file, as demonstrated by
printbuf_memappend.

Also update indentation in hash file (two spaces)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/json-c/json-c.hash

@@ -1,4 +1,4 @@
 # From https://github.com/json-c/json-c/wiki
-sha256 b377de08c9b23ca3b37d9a9828107dff1de5ce208ff4ebb35005a794f30c6870  json-c-0.14.tar.gz
+sha256  b8d80a1ddb718b3ba7492916237bbf86609e9709fb007e7f7d4322f02341a4c6  json-c-0.15.tar.gz
 # Locally calculated
-sha256 74c1e6ca5eba76b54d0ad00d4815c8315c1b3bc45ff99de61d103dc92486284c  COPYING
+sha256  74c1e6ca5eba76b54d0ad00d4815c8315c1b3bc45ff99de61d103dc92486284c  COPYING

package/json-c/json-c.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-JSON_C_VERSION = 0.14
+JSON_C_VERSION = 0.15
 JSON_C_SITE = https://s3.amazonaws.com/json-c_releases/releases
 JSON_C_INSTALL_STAGING = YES
 JSON_C_LICENSE = MIT