util: try to use SSE instructions with MSVC and 32-bit gcc

util: try to use SSE instructions with MSVC and 32-bit gcc

The lrint() and lrintf() functions are pretty slow and make some
texture transfers very inefficient.  This patch makes a better effort
at using those intrisics for 32-bit gcc and MSVC.

Note, this patch doesn't address the use of SSE4.1 with MSVC.

v2: get rid of the ROUND_WITH_SSE symbol, per Matt.

Reviewed-by: José Fonseca <jfonseca@vmware.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>