Merge pull request #1082 from dottedmag/cleanups/allow-no-users-promises

Cleanups/allow no users promises
Add ./testall --gdb option to drop into gdb for acceptance test
Merge pull request #1084 from dottedmag/feature/testall-gdb-option

Add ./testall --gdb option to drop into gdb for acceptance test
mention --printlog option in testall help
Test: read long files (regression after 3.5)
Check compiler name for -Wno-duplicate-decl-specifier

Just passing -Wno-duplicate-decl-specifier does not cause GCC to abort.
Cosmetics
Merge FileRead/FileReadMax into single function

This change simplifies error reporting and avoids unreliable checking
of stat(2) to preallocate buffers.