COMMON: Restore mistakenly deleted line in DumpFile

Fixes Coverity issue #68244.
COMMON: Properly initialize UString:_size in all constructors

Fixes Coverity issues #68234 and 68236.
AURORA: Remove duplicate comparison in isLanguageStandard()

Fixes Coverity issue #68228.
COMMON: Check for seek errors in File::open()

Fixes Coverity issue #68227.
COMMON: Add fallbacks for PRId64/PRIu64

By forcing %lld/%llu and casting to (un)signed long long.
XML: Use PRIu64/PRId64 to print 64-bit GFF types

Should fix Coverity issues #68229 and #68230.
DOCS: Show Travis CI and Coverity Scan badges in the README
COMMON: PRId64/PRIu64 should be string literals