Replace dtoa with fast_float for faster string-to-float parsing

fast_float implements C++17 from_chars for floating-point types, which
is still unavailable even in the latest versions of compilers e.g. for
macOS. It is maintained, unlike dtoa; it is said to be adopted as the
from_chars implementation for gcc. It is header-only, which simplifies
many things.

Change-Id: I6b597d4d35a076930e6e35f4f8cff3ca84f48ba1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/191248
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

codemaker/Executable_cppumaker.mk

@@ -11,12 +11,6 @@ $(eval $(call gb_Executable_Executable,cppumaker))
 
 $(eval $(call gb_Executable_use_external,cppumaker,boost_headers))
 
-ifeq ($(DISABLE_DYNLOADING),TRUE)
-$(eval $(call gb_Executable_use_externals,cppumaker,\
-    dtoa \
-))
-endif
-
 $(eval $(call gb_Executable_use_libraries,cppumaker,\
     unoidl \
     $(if $(filter TRUE,$(DISABLE_DYNLOADING)),reg) \

codemaker/Executable_javamaker.mk

@@ -11,12 +11,6 @@ $(eval $(call gb_Executable_Executable,javamaker))
 
 $(eval $(call gb_Executable_use_external,javamaker,boost_headers))
 
-ifeq ($(DISABLE_DYNLOADING),TRUE)
-$(eval $(call gb_Executable_use_externals,javamaker,\
-    dtoa \
-))
-endif
-
 $(eval $(call gb_Executable_use_libraries,javamaker,\
     unoidl \
     $(if $(filter TRUE,$(DISABLE_DYNLOADING)),reg) \