Improve spelling in error messages

Author: stijnh

src/internal/directives.cpp

@@ -449,7 +449,7 @@ process_directive(TokenStream& stream, KernelBuilder& builder, Context& ctx) {
         } else {
             stream.throw_unexpected_token(
                 t,
-                "this directive is not supported by kernel_launcher");
+                "this directive is not supported by kernel launcher");
         }
     }
 }

src/internal/tokens.cpp

@@ -399,7 +399,8 @@ void TokenStream::throw_unexpected_token(
 
     std::stringstream msg;
     msg << "error:" << file_ << ":" << line_col.first << ":" << line_col.second
-        << ": found invalid token \"" << clean_string(span(begin, end)) << "\"";
+        << ": error occured at token \"" << clean_string(span(begin, end))
+        << "\"";
 
     if (!reason.empty()) {
         msg << ", " << reason;
@@ -422,4 +423,4 @@ std::string TokenStream::span(size_t begin, size_t end) const {
 }
 
 }  // namespace internal
-}  // namespace kernel_launcher
+}  // namespace kernel_launcher

src/pragma.cpp

@@ -32,7 +32,7 @@ KernelBuilder build_pragma_kernel(
 
     throw std::runtime_error(
         "kernel '" + kernel_name + "' was not found in file \'" + filename
-        + "\'");
+        + "\' or was not annotated correctly");
 }
 
 PragmaKernel::PragmaKernel(