Added Android specific includes

[fdelfrari]

Building mosquitto for Android using NDK r25 is working fine. But, when updating to r27 the following error is raised:

[ 79%] Linking C executable mosquitto
[ 79%] Built target mosquitto
[ 80%] Building C object apps/db_dump/CMakeFiles/mosquitto_db_dump.dir/db_dump.c.o
/home/builder/devopsagent/_work/521/s/mosquitto/apps/db_dump/db_dump.c:480:16: error: call to undeclared function 'ntohl'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
480 | db_version = ntohl(i32temp);
| ^
1 error generated.

Adding <sys/endian.h> when build target is Android, fixes the issue.

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