Changing conversion functions to use strtol.
Changing conversion functions to use strtol.

std::stoi is a C++ 11 feature, which is causing problems with the
Android build. Switching to strtol, which works instead.

Tested on Android and Linux (using Gerrit and Zooshi).
PiperOrigin-RevId: 139501159
Change-Id: I3fde60bfc3436887129104b576221c66ecaef4eb

google/flatui,google/flatui,google/flatui,google/flatui