Change configure, compile and install functions

Mozilla build system has changed compared to old Firefox version 10.
For more information about new mozilla build system see
https://developer.mozilla.org/en-US/Firefox



Remove unused variables.

Add SHELL to EXTRA_OEMAKE. Mozilla build system needs pass explicitly
SHELL variable.

Configure variables needed by mozconfig work properly.

Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>