Added -Wshorten-64-to-32 flag to project.mk
Added -Wshorten-64-to-32 flag to project.mk

This flag will trigger warnings on 32 bit builds.
The resolution of those warnings will take place in the coming commits.

The warnings typically represent assignment between incompatible integer types.

int_type_1 x = int_type_2 y;

On a 32-bit build, the warning is triggered if int_type_1 is 32-bit and int_type_2 is 64-bit.
The warning is a sign that the integer types are used incorrectly. Even on a 64-bit build where the two types
would typically both be 64-bit, the code is still suffering from logically incomatible assignments.
Fixing the 32-bit warnings hence leads to nicer code even on 64-bit builds.

realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core