configure.ac: add --enable-profile

configure.ac: add --enable-profile

For profiling mesa's code, especially llvmpipe, PROFILE should be
defined. Currently, this define can only be generated if mesa is
built using scons.
This patch makes it possible to generate this define also when building
mesa through automake tools.

v2:

- Change --enable-llvmpipe-profile to --enable-profile
- Add -fno-omit-frame-pointer to CFLAGS and CXXFLAGS when enabling profile

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>