Abandons the 4-byte stack alignment DR was using for 32-bit x86 Linux (for compatibility with legacy code). The SysV ABI breakage by gcc 4.5 was 10 years ago and in that time other compilers have followed suit, making 16-byte the de facto standard. Clang doesn't even support requesting 4-byte stack alignment. DR is now switching to the modern ABI of 16-byte stack alignment.
Bumps the version to 7.92 and marks OLDEST_COMPATIBLE_VERSION as 791 to indicate the binary compatbility break for 32-bit x86 DR.
Leaves Windows as 4-byte-aligned, since changing the injection assembly code and other pieces would be a bunch of extra work for little benefit: Windows 32-bit only requires 4-byte alignment, and the code is not that much more complex with a split alignment.
Aligns the stack after clean call preparation (state saving) and again after clean call argument setup. Currently the stack restores can end up with two LEA's in a row; we leave removing that for future work.
Adds stack alignment checks to some of the clean call tests.
Updates the manual stack alignment in DR assembly code. I only found a few places to update and I expected to find more. We should monitor usage outside the test suite and look for problems.
Issue: #847 (closed), #3966 (closed), #4200 (closed) Fixes: #3966 (closed) Fixes: #4200 (closed)