SRG files can still be valid even without that check - they may not be mapping complete jars. That belongs in debug log at best.
Don't need that validation either
Expose jarMapping and inheritanceProvider in JarMapping
Add remapClassFile() accepting byte[] instead of InputStream
Initial implementation of field reflection remapper

Remaps the string constant in class.getDeclaredField("fieldname")
Refactor tryClimb() into JarMapping

JarMapping now contains the IInheritanceProvider and tryClimb()
instead of JarRemapper, to allow other remappers access to the
same inheritance traversal code.
Use tryClimb in ReflectionRemapper
Add debug option to ReflectionRemapper
Add RemapperPreprocessor

Used to "preprocess" a class file, using the ASM tree API,
before remapping with JarRemapper. Right now it only
extracts the inheritance and adds to an InheritanceMap.

Code moved from MCPC+ PluginClassLoader.
Combine reflection remapping into RemapperPreprocessor

Allows simultaneously extracting inheritance information,
and remapping reflection -- all in a single pass.