cmake: handle libm, libGL, libGLU and libSDL2 checks consistently

This adds require_{m,gl,glu} functions to build_options.cmake;
consistent with the require_sdl2 function. These are now used to check
dependencies for glxspheres and vogltest.

Except for require_m, all of these functions use cmake's built in
find_path and find_library functions, passing them pkg-config data in as
'HINTS' which, as far as I can tell, seems to be the recommended pattern
for using pkg-config with cmake.

Notably this now means we use pkg-config to look for libGL and libGLU so
developers can optionally manage which specific libraries they build
against using standard pkg-config environment variables on Linux. It's
now also possible to explicitly override the library and include paths
for these as cached cmake variables.
Don't hook shell processes on Linux
Kill amd64 button, preload vogltrace64 and vogltrace32
cmake: support building 32 bit binaries on multilib host

This tries to ensure cmake won't find 64 bit libraries when trying to
build 32 bit binaries on a multilib system by passing -DBUILD_X64=Off

This also passes -m32 as a linker flag

This avoids needing to manually pass a toolchain.cmake file via
-DCMAKE_TOOLCHAIN_FILE=
Merge pull request #81 from rib/rib/multilib-build-fix

cmake: support building 32 bit binaries on multilib host
Don't hook cgdb or gdb
Handle command line argruments with steamlauncher
Add desktop-launcher from Witcher 2
Fix cMsgFlag value
Update README.md
Output more performance data when looping frames
* Report time taken to perform a state snapshot (only when NOT in benchmark mode)
* Report time taken to apply all state snapshots (only when NOT in benchmark mode)
* Report time taken to render all 'initial' frames (always output), (if not in benchmark mode, also includes time to take snapshot)
* Report time taken to render all 'looping' frames (always output)
* Still report 'overall' execution time (includes taking and applying all snapshots if applicable)

* Also minor clean up to code which allowed removal of one level of indentation
Logfile cleanup
- Remove logfile_append.
- Add console::set_log_stream().
- Switch all init_logfile() to use set_log_stream().
- Add some VOGL_CHECK_GL_ERROR calls in handle_context_made_current().
- Initialize logfile very early w/ game pid to help debug launch problems.
- Don't log in dlopen when console hasn't been initialized yet.
Ignore minidump_stackwalk, append to logfiles
Move vogltrace options to vogl_cmdline_opts.h
Rename steamlauncher to vogl_trace
Move vogl_build/bin to vogl_build
formatting cleanup
Fix to CS:GO rendering--uses PMB, needs to capture additional buffer creation method.

Conflicts:
	glspec/gl_wgl_whitelisted_funcs.txt
Compilation warning fix.
Flags parameter should be a reference.