Replace glGenerateMipmapEXT with glGenerateMipmap
Using EXT here is a misnomer
Move source code to src/ subdirectory
Eliminate for loop
Remove leading _ from include guards

Thou shalt not do that
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _
Prefix (m)ember variables with m_ instead of plain _